build: use stdbool.h if available

build: use stdbool.h if available

If stdbool.h is available use it, otherwise create emulation.

basic.h defines a type 'bool' that conflicts with
the altivec keyword bool which has to be fixed upstream, see
bugs[1][2].

[1] https://bugs.gentoo.org/show_bug.cgi?id=293840
[2] https://bugs.gentoo.org/show_bug.cgi?id=297854

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>
Acked-by: David Sommerseth <davids@redhat.com>
Message-Id: 1335528555-13225-1-git-send-email-alon.barlev@gmail.com
URL: http://article.gmane.org/gmane.network.openvpn.devel/6363
Signed-off-by: David Sommerseth <davids@redhat.com>