process.c: move getgroups* and setgroups* parsers to a separate file

* groups.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* process.c: Move sys_setgroups, sys_getgroups, sys_setgroups32,
sys_getgroups32, and related code to groups.c.
diff --git a/Makefile.am b/Makefile.am
index c344338..52f7f46 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -39,6 +39,7 @@
 	get_robust_list.c \
 	getcpu.c	\
 	getcwd.c	\
+	groups.c	\
 	inotify.c	\
 	io.c		\
 	ioctl.c		\