parameter, not an optional string. Also, call new convenience
function that takes res_id's.
* resrc.c (define_control): missing text means zero-length string,
not zero ID.
(define_icon_control): New.
* windres.h: declare define_icon_control.
(main): process verbose option
* resrc.c (look_for_default): new. Look for the default
preprocessor in a given location.
(read_rc_file): for foo/bar-windres, look for foo/bar-gcc,
foo/gcc (in case of foo/windres), and then gcc (the old default).
