Fix missing strnlen problems

Fix missing strnlen (a GNU extension) problems by using qemu_strnlen
used for user emulators also for system emulators.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

cutils.c

@@ -109,6 +109,19 @@ int stristart(const char *str, const char *val, const char **ptr)
     return 1;
 }
 
+/* XXX: use host strnlen if available ? */
+int qemu_strnlen(const char *s, int max_len)
+{
+    int i;
+
+    for(i = 0; i < max_len; i++) {
+        if (s[i] == '\0') {
+            break;
+        }
+    }
+    return i;
+}
+
 time_t mktimegm(struct tm *tm)
 {
     time_t t;