options.c: fix broken unary minus usage

options.c: fix broken unary minus usage

In Visual Studio when unary minus is applied to unsigned,
result is still unsigned. This means that when we use result
as function formal parameter, we pass incorrect value.

Fix by introducing frame_remove_from_extra_frame(),
which makes code semantically more clear and eliminates
the need in negative value and cast.

Since GCC didn't complain (and users too :), it probably performed
cast to signed automatically.

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1539258702-15427-1-git-send-email-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg17739.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>