This reverts commit 04178a28.

This is not needed anymore because cling can bridge well compiled and interpreted worlds.

This reverts commit 5c076c6c.

This reverts commit b406328d, reversing
changes made to 318c7a47.

Replaces if(builtin_foo) statements with explicit support in the
various ROOT macros.

This removes ROOT_ADD_BUILTIN_DEPENDENCIES and adds BUILD_BYPRODUCTS
for the external projects.  This way, the build system can explicitly
depend on the output file of the external project instead of introducing
a hidden dependency..

Make cannot deal with 'export *', they have to be escaped and fixed later on.

This is the recommended way of using the modules feature and should pave our way
of enabling -fmodules-local-submodules-visibility mode.

Use the standard #include <typeinfo> and #include <iosfwd> instead.

This remove duplicate definitions and duplicate default argument errors when
building modules for proof.

Our two build systems can generate almost entirely a modulemap file laying out
one module per library. Due to some non-modular implementation in ROOT's core we
still need to treat some header files specially.

This patch appends modular header files to the modulemap while skipping the
predefined ones. Configure-make relates all headers that are installed in
$ROOTSYS/include to their library whereas relates only headers which are part of
library's dictionary.

rpdutils is under net, not proof

rpdp headers are not part of the ROOT public API and thus should not
be visible in include/. They were simply because multiple ROOT modules
were including them, and we had no way to specify that other than
publishing them. Now we have a new directory next to src/ and inc/:
res/ (as in "reserved" or "restricted"), signalling that these headers
are not public but used by other ROOT modules.

Update the Moduke.mk-s accordingly.

Move a few really private headers into their src/ directories.

Remove residual symlink creation (after optimization introduced in 0a976f4a).
For PROOF-Lite, make sure that all the relevant files (including .pcm) are present in the cache.

Information was not always transmitted

For setups having limitations with open ports, such as in some cases PoD, xproofd provides the
possibility to serve the files produced during running via the same port. This was implemented
by starting a rootd process upon an incoming request for a file. The use of xrootd for this
purpose was not possible with earlier versions of XRootD (up to 3) because the file serving
protocol was not available as separate plug-in.
This patch enables the use of xrootd for this purpose and deprecates the use of rootd .