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

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

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.

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 

Created list was not always deleted correctly

It is provided in all sub-classes, but was not defined in TSQLStatement
class. Strange

civetweb mg_send_file function does not support symbolic links on
Windows, but in some situations it is required. Advantage of
mg_send_file() that it supports partial reading, therefore keep
functionality for ROOT files

One has to use binary mode to be able read file content,
otherwise Windows may change lines ending and 
result will not fit into the preallocated string

Whichever library was missing a link against libatomic in my
Raspberry Pi test build, received a link against ROOT_ATOMIC_LIBS
in this update.

When wrong-formatted TMessage is received, length of buffer may be 0.
As result, buffer may not be allocated at all.
One should avoid that in such case memory is accessed