MSVC apparently does not pack bitfields of different type

...so c963d7e642c24f40c19fb9dc227db5da96728c12 "bool improvements" changed the
size of some structs in sw/source/filter/ww8/ww8struc.hxx that are used for raw
IO and thus have fixed layout requirements.  Reverted that part of the commit
and instead use explicit conversion between bool and sal_uInt16 where necessary.

Also added static asserts for those structs that were easily identifiable as
being used for raw IO.  (Also reverted the bools in some other structs that were
not (easily) identified as being used for raw IO even if that might thus not be
necessary, but better safe than sorry.)

Change-Id: I60e17a2821d67961f50691625999f2aa72c5ebce