[AD] CMake parameter quirks

[Kibiz0r <kibiz0r@xxxxxxxxxx>]

* a5_physfs and ex_physfs don't use PHYSFS CMake params

* ex_curl doesn't use CURL CMake params

* dxguid.lib is linked as just dxguid.lib, while the other DX libs use their CMake paths

* PNG_PNG_INCLUDE_DIR should probably be PNG_INCLUDE_DIR

If I knew CMake I'd fix them myself. (if they are indeed bugs)

--
Michael Harrington | Software Apprentice
Atomic Object | http://atomicobject.com
[Ph] +1 616 776 6020 [Fx] +1 616 776 6015