* app/tools/gimprectangletool.c
* app/tools/gimprectangletool.h
* app/tools/gimprectangleoptions.c
* app/tools/gimprectangleoptions.h: new code for base
class for rectangle tools.
* app/tools/gimpnewrectselecttool.[ch]: modified to
derive from GimpRectangleTool.
* app/tools/Makefile.am: modified accordingly
* app/tools/gimpselectionoptions.[ch]: remove stuff
no longer needed by new rect select tool.
This is work in progress.