ROOT uses builtin unuran sources, but has no switch to use the system
library instead. This adds this missing option.

CMAKE_Fortran_FLAGS is initialized from the FFLAGS environment variable.
If the initial value of CMAKE_Fortran_FLAGS is overwritten, comfiguring
the build using FFLAGS fails.

It leads to incompatible options like:

$ g++ -Werror=format-security -c a.cxx
cc1plus: error: -Wformat-security ignored without -Wformat [-Werror=format-security]

Before -Wall was removed -Wall implied -Wformat, and he options were
compatible:

$ g++ -Wall -Werror=format-security -c a.cxx
(no error)

This commit makes sure also -Werror=* is removed when -Wall is removed.

The old rule also changed e.g. -Werror=format-security to =format-security,
which causes the compilation to fail.

It is no longer used in gcc 6

The configure script currently uses a simple grep to determine if an option
is deprecated. This causes problems, since the enable-reflex option is
deprecated and grepping for enable-r will result in a match. The configure
script therefore considers enable-r deprecated too, even though it is not.
This commit addresses this issue.

 - bin/pq2
 - bin/rootd
 - bin/xpdtest
 - initd and xinitd start-up scripts
 - don't install some private headers

 - Build RFIO using dpm libraries if castor libraries are not available
 - Add additional include and library search paths
 - Add missing glib header path in GFAL module
 - Search also for globus libraries wouthout the flavour in the name
 - Add missing io/hdfs/CMakeLists.txt
 - net/globusauth has no installed headers - remove ROOT_INSTALL_HEADERS()

This slightly changes lookup order: Namely, the system-folder "/usr/include/postgresql"
is now preferred over "/usr/include/" even if both container libpq-fe.h.
This finds the correct path on a standard Gentoo installation, where "/usr/include/postgresql"
is a symlink to the folder with all include-files for the user-selected postgresql-version,
while "/usr/include/libpq-fe.h" is a single symlink provided for backwards-compatibility.

Since ROOT uses also e.g. "pg_config.h", selecting "/usr/include/" over "/usr/include/postgresql"
leads to failure on Gentoo.

Exclude ECompressionAlgorithm from namespace ROOT in C (namespaces are a C++ thing)
that enables using Compression.h in C
Bits.h can then use ECompressionAlgorithm instead of hard coded numbers

Change an example: variable "r" and "b" were wrongly linked by oxygen to other part of the reference guide. We use now variables' names similar to some already used in other examples.

* gbitzes-master:
  TDavixFile: Add support for v4 signatures and STS tokens

Fix ROOT-8221 - Enum value kKey_Shift not accessible from python with ROOT 6. Thanks to Mattias Ellert  for the hint.

ROOT will add -Wall; llvm only suppressed warnings if they are on.

GCC5 ABI patch is in.
This reverts commit 9c2b6c38.

Cling should now be able to do that.

Only build cling as part of llvm if(DEFINED ROOT_BINARY_DIR).

Else we will build it here also for configure/make, because that now uses llvm/CMake, too.

It is needed by the JIT to resolve symbols from the binary.
Fixes rootcling issue on Linux.