[Sorry, forgot to commit my source changes in my previous commit.]

Document all options and general usage.

Implement the -a option to bump the annotation_level.  This improves
the Emacs gud behaviour.  You can now supply the following function

(defun gud-gdb-massage-args (file args) (cons "-a" args))

(e.g. by evaluating it from the *scratch* buffer) and get the normal
jump to the source window when browsing the stack.

We should probably eventually supply our own kgdb submode to gud.el.

gnu/usr.bin/gdb/kgdb/main.c

@@ -80,7 +80,7 @@ usage(void)
 {
 
 	fprintf(stderr,
-	    "usage: %s [-v] [-d crashdir] [-c core | -n dumpnr | -r device]\n"
+	    "usage: %s [-a] [-v] [-d crashdir] [-c core | -n dumpnr | -r device]\n"
 	    "\t[kernel [core]]\n", getprogname());
 	exit(1);
 }
@@ -218,8 +218,11 @@ main(int argc, char *argv[])
 	if (s != NULL)
 		strlcpy(crashdir, s, sizeof(crashdir));
 
-	while ((ch = getopt(argc, argv, "c:d:n:r:v")) != -1) {
+	while ((ch = getopt(argc, argv, "ac:d:n:r:v")) != -1) {
 		switch (ch) {
+		case 'a':
+			annotation_level++;
+			break;
 		case 'c':	/* use given core file. */
 			if (vmcore != NULL) {
 				warnx("option %c: can only be specified once",