allegro/src/keyboard.c: Avoid accessing out of range items in key/_key arrays
Temporal fix for issue 299: Don't allow moving the selection from other editor than the current one
src/app/modules/gfx.cpp: Remove deprecated RectTracker stuff
Move kPaintMessage code to onPaint() event for some widgets

The affected widgets are: ColorBar::ScrollableView, ColorButton, and
StatusBar.

* Added Graphics::drawLine()
* Moved rectgrid and draw_color to modules/gfx.cpp
Fix bug in fixup_image_transparent_colors(): reading pixels out of bounds