Wx3 nightmare v3

Add support of wx3.0 for linux.

Good:
* 2.8 is still working and it is still the default
* --wx30 was added to the build script
* a stripped down version of wx3.0 was uploaded for windows. But I think it can be reduced further
* I didn't find any major regression in both versions.

Bad:
* zzogl is not yet compatible with wx3.0 (maybe fpic related)
* miss wx30 on MSVC
* wx2.8 PCSX2 was hand-tuned by Jake (good luck :p )

Change since v2:
* Revert some interface change see commit 5 & 6 for details. Avoid several regression on drag&drop and path.
* Add a new commit that fix a bad designed code (not directly related to wx3).