* boards/scales/*.png: Complete redraw by Renaud Blanchard

* src/gcompris/bar.c: shifted all buttons on the left to free the home
* src/gcompris/bonus.[ch]: implemented BONUS_RANDOM, changed bonus.h to be an enum
* src/boards/Makefile.am: changed PTHREAD_LIBS by PTHREAD_LIB as it should be
* src/boards/algebra.c change operation order and other fix
* src/boards/draw.c: Corrected a bug where you can delete the white background