hw: make Processor_client::_processor protected

ref #1126
hw: turn Cortex_a9::Processor_driver into a class

ref #1126
hw & rpi: provide Pic::MAX_INTERRUPT_ID

ref #1126
hw & cortex_a9: do lazy FPU-context switch

ref #1126
base & cortex_a9: enable FPU

ref #1126
base: test for the pseudo-parallel use of an FPU

fix #1126
Generic resource monitor (WiP)
os: Construct invalid 'Rect' by default
os: Utility for tracking dirty rectangles
nitpicker: Perform redraw asynchronously

This patch changes nitpicker's way of redrawing. Originally, redraw
operations were triggered immediately by the RPC functions invoked by
clients. In the presence of clients that invoked a large number of those
functions, the server could become overloaded with processing redraw
operations. The new version performs redraw operations out of band with
the RPC functions. Similar to the design of the DOpE GUI server, redraw
operations are processed periodically. The RPC functions merely modify
meta data and track the dirty areas that need to be updated.
Consequently, nitpicker's RPC functions become light-weight operations.

As a nice collateral effect of this patch, nitpicker's internal
structure could be simplified because the drawing backend is no longer
needed by the code that dispatches the RPC interface.
Scout: Add DroidSans-Bold10 font as tff
Minimalistic decorator for window system
decorator stress test
Simple desktop environment (WiP)
fixup desktop (handle parent views across sessions)
backtrace.diff
backtrace_c.diff
issue1132.diff
issue1134.diff
issue1137.diff