OS/2: Cleanup slib_create_def_cmd

Export symbols by name rather then ordinal.
Remove PROTMODE directive as it does not make sense for 32 bit library.
Also silences a warning from some linkers.

Signed-off-by: Dave Yeo <dave.r.yeo@gmail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>