Revert "Use preprocessor macro __ROOTCLING__ instead of __CINT__ in linkdef"
Revert "Use preprocessor macro __ROOTCLING__ instead of __CINT__ in linkdef"

This reverts commit 915d488afd46a8e8199484ab77861bb47d8bac09.

The replacement prevented the recording of the data member documentation
strings for the content of the library and thus was breaking the I/O, in
particular transientness, for thoses classes, eg TTreePerfStats.
(See below for an example).

This seems to be due to the fact that we need/must not add __ROOTCLING__
during the parsing that will be recorded in the the pch, see in
core/dictgen/src/rootcling_impl.cxx line 4334:

    // We do not want __ROOTCLING__ in the pch!
    if (!onepcm) {
       clingArgs.push_back("-D__ROOTCLING__");

So, at least for now, we need to keep using __CINT__ for the LinkDef.h
of the libraries included in the PCH.

See:

root [0] TClass::GetClass("TTreePerfStats")->GetStreamerInfo()->ls()

StreamerInfo for class: TTreePerfStats, version=7, checksum=0x1f86d003
  TVirtualPerfStats BASE            offset=  0 type= 0 ABC for collecting PROOF statistics
  int            fTreeCacheSize  offset= 16 type= 3 TTreeCache buffer size
  int            fNleaves        offset= 20 type= 3 Number of leaves in the tree

vs

root [0] TClass::GetClass("TTreePerfStats")->GetStreamerInfo()->ls()

StreamerInfo for class: TTreePerfStats, version=6, checksum=0x84181ab4
  TVirtualPerfStats BASE            offset=  0 type= 0 ABC for collecting PROOF statistics
  int            fTreeCacheSize  offset= 16 type= 3
  int            fNleaves        offset= 20 type= 3

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