res_fax: Fix out of bounds error in update_modem_bits().

ASTERISK-24357 #close
Reported by: Jeremy Laine
Patches:
      res_fax_bounds.patch (license #6561) patch uploaded by Jeremy Laine
	  Modified patch to not use magic numbers.
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Merged revisions 423979 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 423983 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 423987 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@423992 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_fax.c

@@ -809,7 +809,7 @@ static int update_modem_bits(enum ast_fax_modems *bits, const char *value)
 		m[i] = NULL;
 	} else {
 		tok = strtok(v, ", ");
-		while (tok && (i < 5)) {
+		while (tok && i < ARRAY_LEN(m) - 1) {
 			m[i++] = tok;
 			tok = strtok(NULL, ", ");
 		}