Update localplt.data for powerpc-nofpu.

Update localplt.data for powerpc-nofpu.

Testing for powerpc-nofpu showed that localplt.data was out of date.
Two new soft-fp functions showed up in the list: __gtsf2 and
__unordsf2; this patch adds these as optional.  __signbit and
__signbitl no longer appear as local PLT entries; given the move to
__builtin_signbit* for all GCC versions supported for building glibc
(and given the use of the type-generic signbit macro within glibc),
those can safely be removed from the list, which this patch does.

Tested for powerpc-nofpu.

	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/localplt.data
	(__gtsf2): Add as optional for libc.so.
	(__unordsf2): Likewise.
	(__signbit): Remove for libc.so.
	(__signbitl): Likewise.