Otherwise we cannot "prepare" the pin state before setting the mode so
that the pin comes up in the required 1/0 state rather than the default state (0).
There are two color formats in HAL.Bitmap, the Bitmap_Color (with Alpha,
Red, Green, Blue components) and the "native" raw value of the pixel.
In the current interface users select a color for each operations (Fill,
Draw_Line, Draw_Circle, etc.) which means each operation has to be
declared twice, one with a Bitmap_Color and one with native pixel value.
Inspired by the Cairo graphics library, this patch add a Set_Source
primitive which allows to specify the color that will be use. Each
drawing operation then uses this color for rendering.
This simplifies the interface since drawing operation only have to be
declared once. It may also allow for more advanced sources in the future
like gradients or textures.
This merges the various sdcard handling enhancements into a single commit,
the two branches master and sdcard having diverged too much to perform
a simple git merge.
