debugger: rework dumping arrays of plain data

Simple array data can be fetched in one go.
The "normal" way gdb asks the server for contents is one item
at a time, at ~3ms per round trip. Now we get 2000 in 200ms.

This also introduces a re-usable readRawMemory function and
removes a few checkAccess calls which will be triggered anyways.

Change-Id: Ic07a3d6593fd2ea45f7a8058509118fe22a845bb
Reviewed-by: hjk <qthjk@ovi.com>