#544 wrong default search path on W32

[IOhannes m zmölnig]

on W32, Pd uses some default search-paths (outside of the Pd-dir), where users can install libraries,... either globally or per-user. the details are explained in the puredata wiki, but in short it is an attempt to use the standard application data paths as provided by W32.

Unfortunately it seems that Pd has hardcoded parts of these application data paths, rather than using the officially defined envvars.
i guess this has worked OK for XP, but stopped working properly since W7, namely.

The attached patch (apply with git am 0001-Use-*-dat.patch) fixes this by using envvars that expand to the standard paths.