1) minor modifications in fileconf.cpp

1) minor modifications in fileconf.cpp
2) new MSW function (private.h): wxGetWindowText() which works with wxString
   instead of (horror) fixed size buffers. All calls to ::GetWindowText()
   should be replaced with this!
3) remains of casts to float in different wxControl classes removed,
   (EDIT|BUTTON)_HEIGHT_FROM_CHAR_HEIGHT macros introduced (could be
   made inline functions as well...)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@765 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775