[physfs] Win32 build

[Brian Hook]

I've updated the INSTALL to reflect the changes.  Also, the DLL build 
doesn't support MVL or HOG by default (I didn't want to modify it), 
but the LIB build does.

I cast away a warning in the hog driver.

I now default the static LIB to supporting all file formats to avoid 
any "bug" reports where it doesn't find a QPAK file because the driver 
isn't compiled in.

Was still building the final product in Debug/ instead of 
physfs_static_debug, etc.

Brian