Configury changes for obstack optimization

Configury changes for obstack optimization

Provides defines used to determine whether glibc obstacks are
compatible.  Generally speaking, 32-bit targets won't need to use
obstack.o from libiberty if glibc is used, while 64-bit targets will,
until glibc gets the new obstack code.

libiberty/
	* configure.ac: Get size of size_t.
	* config.in: Regenerate.
	* configure: Regenerate.