[PATCH] refactor strspn/strcspn macro

[Roland McGrath]

Use a less opaque name, e.g. __maybe_builtin_strcspn.

Your log entry lacks appropriate whitespace, punctuation, and detail.
A good entry for just the strcspn part looks like:

	* string/bits/string2.h [!_HAVE_STRING_ARCH_strcspn || _FORCE_INLINES]
	[!_HAVE_STRING_ARCH_strcspn] (__maybe_builtin_strcspn): New macro,
	defined differently under [__GNUC_PREREQ (3, 2)] and not.
	[!_HAVE_STRING_ARCH_strcspn] (strcspn): Consolidate variant
	definitions into one that calls __maybe_builtin_strcspn.