The configuration script check for libusb-1.0 availability first and only
if not found check for libusb-0. So if both libraries are installed on the
system the build script will use libusb-1.0
It's possible to force compiling with libusb-0 with the --enable-libusb0 switch.
If the driver support only libusb0 the script check anly for it.

Change-Id: I7eb045d4e2bd553abefad53f3f4023ff46b0f5f6
Signed-off-by: Mauro Gamba <maurillo71@gmail.com>
Reviewed-on: http://openocd.zylin.com/33
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>