ACPICA: Update for new gcc-4 warning options

Added several new options for the gcc-4 generation, and updated
the source accordingly. This includes some code restructuring to
eliminate unreachable code, elimination of some gotos, elimination
of unused return values, and some additional casting.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>