Debugger: Add memory views.

Add a separate memory view tool window available
from the context menus of:

Locals view:
   If the debugger provides size information, colors the
   areas of member variables for inspecting class layouts.

Registers view:
   Tracks the area pointed to by a register.

The view has a context menu allowing to open subviews
referenced by the pointer at the location using
the toolchain abi's word with/endianness.

Rubber-stamped-by: hjk