Throughout, (mainly in fhandler*) fix remaining gcc 4.7 mismatch

warnings between regparm definitions and declarations.
* smallprint.cc (__small_vswprintf): Conditionalize declaration and
setting of l_opt for only x86_64.
* spawn.cc (child_info_spawn::worker): Remove unused 'pid' variable.
* thread.cc (verifyable_object_isvalid): Temporarily define as
non-inline with gcc 4.7+, regardless of target.

winsup/cygwin/tty.cc

@@ -85,7 +85,7 @@ tty::init_session ()
     cygheap->fdtab.get_debugger_info ();
 }
 
-int __stdcall
+int __reg2
 tty_list::attach (int n)
 {
   int res;