Add a -v flag to source-file to show the commands and line numbers.

tmux.h

@@ -1324,6 +1324,7 @@ struct cmd_parse_input {
 #define CMD_PARSE_QUIET 0x1
 #define CMD_PARSE_PARSEONLY 0x2
 #define CMD_PARSE_NOALIAS 0x4
+#define CMD_PARSE_VERBOSE 0x8
 
 	const char		*file;
 	u_int			 line;