In normal situation websockets tried first and only if fails,
fallback to longpoll. WebGui.WSLongpoll: yes in rootrc file
force longpoll from the beginning.
Handle all RWebWindow parameters in one place.
Provide WSKind and WSPlatform methods for THttpCallArg
Harmonize boolean flags handling in RWebWindowsManager

"READ" is default mode and assigned if none of other modes are
recognized. No need for extra `read` flag.

Memory can be leaked in case of any network error

Unused variables, potential memory leak, wrong strlcpy arguemnt

Allocated memory should be cleanup with `free` function.
In all three places where it was used it was wrong.
Either `delete` or `delete []` or just do nothing.

Co-authored-by: Philippe Canal <pcanal@fnal.gov>

Discovery schema: https://github.com/WLCG-AuthZ-WG/bearer-token-discovery/blob/master/specification.md
(adopted based on implementation in htcondor/htcondor.git by bbockelm)

When different subtimes want to load JSROOT, only central
version will be accessed. Let properly use browser cache
when desired

If default page requested in WS-only mode,
THttpServer will present simple list of WS handlers
which is typically web windows, Clicking on each page,
one could get connection to that widget

In such mode only requests for websocket-handlers are allowed.
And if connection token is configured, such connection only
can be established by providing the token.

Delete THttpServer copy constructor

Need to be compiled also with c++11 (without root7)

While now many threads can be used for FastCGI requests
processing, some of these threads can be blocked by postponed
requests. Only when number of free (waiting) threads will be low,
requests should be processed immediately - which is supoprted
by LongPollSocket implementation

Can improve significantly performane, especially when during
web page loading mant js/html/css files can be loaded in parallel

Prepare to multithreaded FastCGI implementation

When configured, any connection request should provide
"token" URL parameter with correspondent value otherwise
connection will be refused

Unfortunately, web sockets are not supported and therefore
should not be tried by clients

They cannot be hold and postponed while FastCGI can only process
single request a time. Therfore such requests should be handled
immediately. For such case LongPollEngine should have simple
buffering inside.

While it enabled by default, it makes problem when
http request includes full URL. Causes problem described in

https://root-forum.cern.ch/t/serving-files-with-thttpserver/42850

When civetweb function used to provide file, mg_send_mime_file will
be used now. It set content type based on extension, recognized by
THttpServer.

Add support of woff/woff2 extensions, which font file used in openui5

If exe.json?method=MethodName was requested without any
extra arguments, such request was ignored.
But one can call obj->MethodName(""); in this case.
Now fixed

Since Apache 2.4 FastCGI is built-in module, but has different
parameter name for URL - SCRIPT_FILENAME. Old parameter PATH_INFO
is used by other FastCGI implementations

* Fix \file references in doxygen markup

* Fix various "end of ..." warnings from doxygen.

This addresses warnings like:

- end of comment block while expecting command </b>
- end of comment block while expecting command </em>
- end of comment block while expecting command </pre>
- end of comment block while expecting command </s>
- end of comment block while expecting command </sup>
- end of comment block while expecting command </tt>
- end of comment block while expecting command </u>
- end of list marker found without any preceding list items
- found </em> tag without matching <em>
- found </li> tag without matching <li>
- found </pre> tag without matching <pre>
- found </sub> tag while expecting </sup>
- found </sup> tag without matching <sup>
- found </tt> tag without matching <tt>
- found </ul> tag without matching <ul>
- illegal </br> tag found
- reached end of file while inside a 'code' block!
- reached end of file while still inside a (nested) comment.
- unexpected end of comment while inside <a href=...> tag
- unexpected end of comment while inside <ul> block
- unexpected html tag <blockquote> found within <h1> context
- unexpected tag </h2> found
- unexpected tag </h3> found
- unsupported xml/html tag <it> found
- unsupported xml/html tag </it> found

* Adjust parameter names in doxygen markup so they match the code

Addresses warnings:

argument '<name>' of command @param is not found in the argument list
of <function>.

* Add missing underscore

* Make the name of macro match the filename

Fixes:

warning: Failed to call `rs302_JeffreysPriorDemo()` to execute the macro.
Add this function or rename the macro. Falling back to `.L`.

* Remove random control character in documentation file

* Remove /** comments */ from md files

* Fix a shadow warning.

Co-authored-by: Stephan Hageboeck <stephan.hageboeck@cern.ch>

The old client library libXrdClient is removed.
Also XrdSysDNS is removed.

Do not build the legacy XProofD file server and client (already
disabled by default - give error if someone enables it while building
with xrootd 5).

Do not build the old libNetx.

Build the new libNetNG without XrdSysDNS, use XrdNetAddr instead.

Provide standard includes where required

Includes like "strlcpy.h" and "snprintf.h" are provided via Rtypes.h,
but really used only in part of the sources. Before removing them
from Rtypes.h (in dev builds) provide them all in required places

Try to exclude as much as possible ${CMAKE_BUILD_DIR)/include from includes paths.
By this one much better control library dependencies - includes from other ROOT libraries not "visible" during the build.

Several generated files placed first to ${CMAKE_BUILD_DIR)/ginclude and then copied to include.

Dictionary generation still uses only ${CMAKE_BUILD_DIR)/include

Co-authored-by: Axel Naumann <Axel.Naumann@cern.ch>

In many places incldues are not required for the dictionary generation, 
therefore target_include_directories can be used