Since C++ typeinfo objects are currently not guaranteed to be merged at

Since C++ typeinfo objects are currently not guaranteed to be merged at
runtime by the dynamic linker, check for their equality in libcxxrt by
not only comparing the typeinfo's name pointers, but also comparing the
full names, if necessary.  (This is similar to what GNU libstdc++ does
in its default configuration.)  The 'deep' check can be turned off again
by defining LIBCXXRT_MERGED_TYPEINFO, and recompiling libcxxrt.

Reviewed by:	theraven
MFC after:	3 days