libiberty.h (ASTRDUP): New macro.

include:
	* libiberty.h (ASTRDUP): New macro.
	libiberty_optr, libiberty_nptr, libiberty_len): Declare.

libiberty:
	* alloca.c (libiberty_optr, libiberty_nptr, libiberty_len):
	Define.

gcc:
	* c-aux-info.c (affix_data_type): Use ASTRDUP in lieu of
	alloca/strcpy.

From-SVN: r45657