Const-ify the world (or at least a good part of it)

This patch adds 'const' tags to a number of Asterisk APIs where they are appropriate (where the API already demanded that the function argument not be modified, but the compiler was not informed of that fact). The list includes:

- CLI command handlers
- CLI command handler arguments
- AGI command handlers
- AGI command handler arguments
- Dialplan application handler arguments
- Speech engine API function arguments

In addition, various file-scope and function-scope constant arrays got 'const' and/or 'static' qualifiers where they were missing.

Review: https://reviewboard.asterisk.org/r/251/



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@196072 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/vcodecs.c

@@ -1113,7 +1113,7 @@ struct _cm {    /* map ffmpeg codec types to asterisk formats */
 	//struct video_codec_desc *codec_desc;
 };
 
-static struct _cm video_formats[] = {
+static const struct _cm video_formats[] = {
         { AST_FORMAT_H263_PLUS, CODEC_ID_H263,  CM_RD }, /* incoming H263P ? */
         { AST_FORMAT_H263_PLUS, CODEC_ID_H263P, CM_WR },
         { AST_FORMAT_H263,      CODEC_ID_H263,  CM_RD },
@@ -1137,7 +1137,7 @@ static enum CodecID map_video_format(uint32_t ast_format, int rw)
 }
 
 /* pointers to supported codecs. We assume the first one to be non null. */
-static struct video_codec_desc *supported_codecs[] = {
+static const struct video_codec_desc *supported_codecs[] = {
 	&h263p_codec,
 	&h264_codec,
 	&h263_codec,