Fix non-__GNUC__ definitions of __inline and __restrict (bug 17721).

Bug 17721 reports that the non-__GNUC__ definitions of __inline and
__restrict are suboptimal, in that they are defined to empty when they
could be defined to inline and restrict for appropriate language
versions.  This patch makes those fixes.

Tested for x86_64 (however, I have not done any testing with an actual
non-__GNUC__ compiler and it's likely such compilers may have other
problems with glibc headers).

	[BZ #17721]
	* misc/sys/cdefs.h [!__GNUC__ && (__cplusplus || (__STDC_VERSION__
	&& __STDC_VERSION__ >= 199901L))] (__inline): Define to inline.
	[!__GNUC_PREREQ (2,92) && __STDC_VERSION__ && __STDC_VERSION__ >=
	199901L] (__restrict): Define to restrict.