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

codecs/codec_gsm.c

@@ -283,7 +283,7 @@ int load_module(void)
 	return res;
 }
 
-char *description(void)
+const char *description(void)
 {
 	return "GSM/PCM16 (signed linear) Codec Translator";
 }
@@ -293,7 +293,7 @@ int usecount(void)
 	return me.usecnt;
 }
 
-char *key()
+const char *key()
 {
 	return ASTERISK_GPL_KEY;
 }