c99_functions.c: Add function prototypes to avoid warnings from -Wstrict-prototypes...

	* intrinsics/c99_functions.c: Add function prototypes to avoid
	warnings from -Wstrict-prototypes -Wmissing-prototypes.  On Tru64
	work around a brain-dead libm by redirecting calls to cabs{,f,l}
	to a local __gfc_cabs{,f,l}.

From-SVN: r109646