Don't fast forward past the end of a message.

This is nice change for users of the voicemail application.  If someone gets a
little carried away with fast forwarding through a message, they can easily
get to the end and accidentally exit the voicemail application by hitting the
fast forward key during the following prompt.

This adds some safety by not allowing a fast forward past the end of a message.

(closes issue #14554)
Reported by: lacoursj
Patches:
      21761.patch uploaded by lacoursj (license 707)
Tested by: lacoursj


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@203785 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/file.c

@@ -1236,7 +1236,14 @@ static int waitstream_core(struct ast_channel *c, const char *breakon,
 				} else {
 					res = fr->subclass;
 					if (strchr(forward,res)) {
+						int eoftest;
 						ast_stream_fastforward(c->stream, skip_ms);
+						eoftest = fgetc(c->stream->f);
+						if (feof(c->stream->f)) {
+							ast_stream_rewind(c->stream, skip_ms);
+						} else {
+							ungetc(eoftest, c->stream->f);
+						}
 					} else if (strchr(rewind,res)) {
 						ast_stream_rewind(c->stream, skip_ms);
 					} else if (strchr(breakon, res)) {