linuxthreads.old: pass back up saved_errno value in manager init
This matches the newer linuxthreads code, and fixes the build warning:
libpthread/linuxthreads.old/manager.c: In function 'pthread_handle_create':
libpthread/linuxthreads.old/manager.c:487:7: warning:
variable 'saved_errno' set but not used [-Wunused-but-set-variable]
Signed-off-by: Mike Frysinger <vapier@gentoo.org>