common: New functions get_option_value and ascii_strupr.

* common/server-help.c (get_option_value): New.
* common/stringhelp.c (ascii_strupr): New.

(cherry picked from commit e2f18023b3b3b7e55b35218f65e37448d1011172)

This might come handy when we eventually backport other changes.

• Signed-off-by: Werner Koch <wk@gnupg.org>