xkb: fix check for appending '|' character when applying rules

There are two ways to separate multiple files in XKB include statements:
'+' will cause the later file to override the first in case of conflict,
while '|' will cause it augment it (this is done by xkbcomp). '!' is
unrelated here.
Currently, if someone tries to use '|' in a rule instead of '+', it
won't have any effect. Since '|' is practically never used, this wasn't
noticed.

Signed-off-by: Ran Benita <ran234@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

xkb/maprules.c

@@ -578,7 +578,7 @@ static void
 Apply(const char *src, char **dst)
 {
     if (src) {
-        if (*src == '+' || *src == '!') {
+        if (*src == '+' || *src == '|') {
             *dst = _Concat(*dst, src);
         }
         else {