Fix compilation warning + C++11 error.
changes in configure for libc++ support.

1) renamed option from --enable-libcxx11 to --enable-libcxx
2) automatically turn on --enable-libcxx when compiling with clang and C++11.
3) check for compatibility in external C++ libraries to be linked against
   libc++. Libraries linked with incompatible run-time are skipped (typically
   xrootd, pythia8 and oracle instant client libs).
mention Manuel Schiller's contributions to RooFit.
1. Replace 'nullptr' with 0.

2. XLFD family names (which are not exactly post script names) are now
generating annoying warnings in Core Text - map XLFD names to post script names.
fix for changed libcxx11 to libcxx option.
1. Fix (kind of) for a deprecation warning in 10.9 - SetFrontProcess

is deprecated now, must be replaced with activateIgnoringOtherApps
(which is not exactly the same though and has probably some funny side-effects).
2. Z-order for a child borderless window is broken after (for example) switching between applications.
No need in ifdefs, the thing is broken in 10.8.5 also.
Ufff, problem had nothing to do with a borderless :)

Context menu in a canvas was never transient :)
Include class names in error messages, even if it is complex to get them.
Fix a comment.
Fix const-cast warning.
Fix NULL returns.