configure: give check_for() the ability to test several item types at once

Currently, check_for() can only test one of prog, inc or lib at once. This patch
removes this limitation.

Signed-off-by: "Benoît THÉBAUDEAU" <benoit.thebaudeau@advansee.com>

 reporter_name="dsreed on freenode/#crosstool-ng"

 reporter_url=""

 reporter_comment="Enables experimental support for VFP/NEON hardware floating point."