constify the return value of reason2str

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@79176 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/channel.h

@@ -1458,14 +1458,12 @@ int ast_channel_whisper_feed(struct ast_channel *chan, struct ast_frame *f);
  */
 void ast_channel_whisper_stop(struct ast_channel *chan);
 
-
-
 /*!
   \brief return an english explanation of the code returned thru __ast_request_and_dial's 'outstate' argument
   \param reason  The integer argument, usually taken from AST_CONTROL_ macros
   \return char pointer explaining the code
  */
-char *ast_channel_reason2str(int reason);
+const char *ast_channel_reason2str(int reason);
 
 
 #if defined(__cplusplus) || defined(c_plusplus)

main/channel.c

@@ -2919,7 +2919,7 @@ int ast_set_write_format(struct ast_channel *chan, int fmt)
 			  &chan->writetrans, 1);
 }
 
-char *ast_channel_reason2str(int reason)
+const char *ast_channel_reason2str(int reason)
 {
 	switch (reason) /* the following appear to be the only ones actually returned by request_and_dial */
 	{