eschema, pcbnew and cvpcb did not find libraries when they were in the default library path, but in a subdirectory

listboxes.cpp problem: apply to window version only. Some other very minor enhancements and bug fixes

Use wxWindowDC instead of wxClientDC as function parameters since we cannot assume that wxPaintDC inherits from wxClientDC

Use full path to executables under Mac OS X, this is because the Mac OS X app launcher doesn't support classic cmd-line parameters