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

llvm-svn: 245514