Fix the layout of bitfields in ms_struct unions: their

Fix the layout of bitfields in ms_struct unions: their
alignment is ignored, and they always allocate a complete
storage unit.

Also, change the dumping of AST record layouts: use the more
readable C++-style dumping even in C, include bitfield offset
information in the dump, and don't print sizeof/alignof
information for fields of record type, since we don't do so
for bases or other kinds of field.

rdar://22275433

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@245514 91177308-0d34-0410-b5e6-96231b3b80d8