rename foreign_option() and move it up

rename foreign_option() and move it up

Add setenv_ prefix to foreign_option funtion so it is more obvious what
it does. Move it further up within options.c, so it is defined before
all future callers. Also declare all argv strings const.

Signed-off-by: Heiko Hund <heiko@ist.eigentlich.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20220527012457.1819262-4-heiko@ist.eigentlich.net>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg24436.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>