parser: add rttime rlimit support

This patch adds support for the rttime rlimit (aka RLIMIT_RTTIME),
available since the 2.6.25 kernel, according to the getrlimit(2)
man page; see that man page for more details on this rlimit.
An acceptance test is also added, as well as an update to the
apparmor.vim input template.

While reviewing to see what made sense in apparmor.vim for the rttime
rlimit, I discovered that RLIMIT_RTTIME's units are microseconds, not
seconds like RLIMIT_CPU (according to the setrlimit(2) manpage). This
necessitated not sharing the case switch with RLIMIT_CPU. I didn't add
a keyword for microseconds, but I did for milliseconds. I also don't
accept any unit larger than minutes, as it didn't seem appropriate
(and even minutes felt... gratuitous). I would appreciate feedback
on what keywords would be useful here.

Patch History:
  v1: initial submission
  v2: - add apparmor.vim support for rttime keyword
      - adjust RLIMIT_TIME value assignment due to its units being
	microseconds, not seconds, and add milliseconds keyword.

Signed-off-by: Steve Beattie <steve@nxnw.org>
Acked-by: John Johansen <john.johansen@canonical.com>

parser/parser_misc.c

@@ -174,6 +174,9 @@ static struct keyword_table rlimit_table[] = {
 #endif
 #ifdef RLIMIT_RTPRIO
 	{"rtprio",		RLIMIT_RTPRIO},
+#endif
+#ifdef RLIMIT_RTTIME
+	{"rttime",		RLIMIT_RTTIME},
 #endif
 	/* terminate */
 	{NULL, 0}