* configure.in: For *-*-cygwin32*, add a -I for winsup to both
XCINCLUDES and XCXXINCLUDES.
* config.shared: Use ${host_includes} when setting CXXINCLUDES in
the DOING_LIBGXX case.
* Makefile.in (_G_config.h): Pass $(CINCLUDES) in CC and
$(CXXINCLUDES) in CXX when running gen-params.
* config.shared (THIS_FILE): Really found via TOLIBIO instead
of TOLIBCXX, which is empty when configuring gperf.
(LIBS): When linking gperf, find libstdc++ relative to TO_TOPDIR
instead of hardcoded "../".
From-SVN: r18168
