Issue corrected.

When window is moved the scroll bar on text box paint the background of
scroll bar. This issue is no more present.
Example projects splited
Add a virtual keyboard that can be placed inside or outside a window.
A simple example project using mSDK and uGUI.

Uncoment #define test1 to use this example.
A simple example project using mSDK and uGUI.

Uncoment #define test2 on main.h to use this example.
To select features of example projects.
Adapt window library to work on limited boxes, like multiple layers.

This feature is added to be capable to work with a header and the
virtual keyboard without interference between them.
Delete unused variable from tRectangle structure.
Optimizing "picturebox_copy_rectangle" function, to skip tryyng to copy rectangle if the destination is outside the visible region.
Update of AM335x, DevKit8600 example project.