Display ?? in memory view for invalid addresses
Merge branch 'master' of https://github.com/hrydgard/ppsspp into MemView

Conflicts:
	Windows/Debugger/CtrlMemView.cpp
Win32: Set current directory at startup to where the exe is.

Fixes the "out-of-the-box" experience in MSVC.
Merge pull request #3426 from Kingcom/MemView

Highlight invalid addresses in memory view
Fix some unicode bugs (open file dialog)