file checks: Merge warn_if_group_others_accessible() into check_file_access()

file checks: Merge warn_if_group_others_accessible() into check_file_access()

Commit 825e2ec1f358f2e8 cleaned up the usage of
warn_if_group_others_accessible()
and moved it into options.c.  At this point there is only one caller of
this
function, check_file_access().

This takes that clean-up one step further and merges everything into
check_file_access().  In addition it removes some no longer needed #ifdefs
and uses platform_stat() to allow a similar check to happen on the Windows
platform as well.

Signed-off-by: David Sommerseth <davids@openvpn.net>
Acked-by: Steffan Karger <steffan.karger@fox-it.com>
Message-Id: <1479163508-19435-1-git-send-email-davids@openvpn.net>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg13062.html