Simplifying the FIELD_* and FRAME_* macros.  Before calling these macros,
you should #define FT_STRUCTURE to the structure which will be filled.

Replaced FT_FIELD_REF with FT_FIELD_SIZE, FT_FIELD_SIZE_DELTA, and
FT_FIELD_OFFSET to make the code more readable; additionally, it should be
more portable because we no longer cast a pointer to an FT_UShort (which
e.g. fails with Sun's C++ compiler) but computes the difference between two
pointers which is guaranteed to work.

Fixing warnings (and C++ errors) while using Sun's latest cc and CC
incarnations.  Most of them are related to variable shadowing.