since the module API is changing, it's a good time to const-ify the description() and key() return values

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@18552 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_snmp.c

@@ -128,12 +128,12 @@ int usecount(void)
     return 0;
 }
 
-char *key(void)
+const char *key(void)
 {
     return ASTERISK_GPL_KEY;
 }
 
-char *description(void)
+const char *description(void)
 {
     return MODULE_DESCRIPTION;
 }