Joseph Carter
There's a whole set of configure tests for BSD's libusbhid, and they only matter on BSD. However, if you have the library on Linux, it gets pulled in as library bloat. And it's bloat of the highest order since not a single function call to the library is ever made unless you're on a *BSD.
If ac_x_libraries is empty it means that the library's found in the default path,
so we skip adding it to the XLIB variable as it screws up the search path.
