make sys/procfs.h mostly work on most archs

these structures are purely for use by trace/debug tools and tools
working with core files. the definition of fpregset_t, which was
previously here, has been removed because it was wrong; fpregset_t
should be the type used in mcontext_t, not the type used in
ptrace/core stuff.

arch/mips/bits/user.h

@@ -7,3 +7,7 @@ struct user {
 	unsigned long magic;
 	char u_comm[32];
 };
+#define ELF_NGREG 45
+#define ELF_NFPREG 33
+typedef unsigned long elf_greg_t, elf_gregset_t[ELF_NGREG];
+typedef double elf_fpreg_t, elf_fpregset_t[ELF_NFPREG];