Touching all the candy again: [Alex Jackson]

Fixed an annoying inconsistency between memory_share and memory_region:
the width() method of the former returned the width in bits (8, 16, 32 or 64)
while the width() method of the latter returned the width in bytes
(1, 2, 4 or 8). Now both classes have a bitwidth() method and a bytewidth()
method. Updated all callers to use whichever one was more appropriate.

Removed the implicit-cast-to-any-integer-pointer ability of memory_regions,
which was rather unsafe (if you weren't careful with your * operators and
casts it was easy to accidentally get a pointer to the memory_region object
itself instead of to the data, with no warning from the compiler... or at
least I kept doing it) Updated all devices and drivers that were accessing
regions that way to use a region_ptr_finder when possible, and otherwise to
call base() explicitly.