Apply patch from solar to also create a tslib.pc.

Apply patch from solar to also create a tslib.pc.

tslib-$LT_RELEASE.pc will die in a future version, as it's unnecessary.
They'll both stay around for version 1.1 and 1.2.  1.3 or higher will remove
it, unless there's a real need (unlikely).

Signed-off-by: Chris Larson <clarson@kergoth.com>