gpg: Add level 16 to --gen-random

* g10/gpg.c (main): Add that hack.

This is an yet undocumented hack to allow printing hex encoded random
number with gpg. The level is forced to be 1 which is is good for
almost all uses. Note that --armor is ignored.

Backported-from-master: d847f0651ab4304129145b55353501636b4e4728

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