* Makefile.in: Add with_cross_host to allow more granular checks.

	* Makefile.in: Add with_cross_host to allow more granular checks.
	Set installation directories accordingly.  Override CC setting only
	if building a Cygwin target.
	* aclocal.m4: Regenerate.
	* configure.in: Move AC_CANONICAL_SYSTEM check up.  Add
	GCC_NO_EXECUTABLES.  Substitute with_cross_host in depending files.
	Test AC_ALLOCA only if building on a native system.
	* configure: Regenerate.