Don't use -Wno-uninitialized in math/.

Don't use -Wno-uninitialized in math/.

The uninitialized variable warnings in math/ having been fixed for all
the supported floating-point formats, this patch removes the use of
-Wno-uninitialized there, continuing with the goal of avoiding -Wno-
options in makefiles as far as possible..

Tested for x86_64 and x86 (full build and testsuite runs), and for
powerpc and mips64 (verified that glibc builds without errors).

	* math/Makefile (CFLAGS): Don't add -Wno-uninitialized.