Fix incorrect quoting which meant action-if-not-found was never executed; check for both the header and the libraries.
Fix issue where pkg-config being unavailable caused pkg-config package tests to fail without triggering an error.
Fix spurious argument within BT_CHECK_LIBUUID which meant action-if-found was invalid
Fix erroneous have_uuid which should be have_libuuid
Add BT_CHECK_LIBDL, et al