* app/brush_generated.c: more carefull when the active brush
	  changes
	* app/docindexif.c: white_space() was ungetch'ing the eof
	  marker which can clear the eof flag on some systems.
	* app/docindex.c: check for ferror()s
	* app/brush_select[ch]: sensitize the edit button iff the
	  active brush is a generated brush.