Remove ancient workaround

This commit removes a workaround for a bug in glibc 2.1.3, which
was released 2000-02-24 and superseded 2000-11-09.

gdb/ChangeLog:

	* gdb_proc_service.h (gdb_prfpregset_t): Remove typedef.
	* proc-service.c (ps_lgetfpregs, ps_lsetfpregs): Use
	prfpregset_t instead of gdb_prfpregset_t.
	* configure.ac (PRFPREGSET_T_BROKEN): Remove check.
	* configure, config.in: Rebuild.