apcupsd: fix configure failure

configure looks in host paths for X, so disable X. This fixes:

	ERROR: This autoconf log indicates errors, it looked at host include and/or library paths while determining system capabilities.

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>