This just adds a warning for bitfields placed next to other bitfields
where the underlying type has different storage. Under the MS struct
bitfield packing ABI such bitfields are not packed.
The patch ensures that a new storage unit is created when the new bitfield's
size is wider than the available bits.
rdar://36343145
Differential Revision: https://reviews.llvm.org/D42660
llvm-svn: 323921
