* cppmacro.c (STDC_0_IN_SYSTEM_HEADERS): Define to 0 if
	undefined.  Remove #ifdef check.
	* config/i386/sol2.h, config/rs6000/sol2.h, config/sparc/sol2.h:
	Define STDC_0_IN_SYSTEM_HEADERS to 1.

From-SVN: r37163