Use 'unsigned int' instead of enum bit-fields to silence some warnings from r321622

  - bots were complaining that the bit-field width was less than the width of the underlying type (note, underlying types of enums can not be bit-fields)
  - add static_asserts for TSS and TSW to ensure that the bit-fields can hold all the enumerators - and add comments next to the last enumerator warning not to reorder.

See https://reviews.llvm.org/rC321622 for the patch that introduced the warnings.

  

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@321625 91177308-0d34-0410-b5e6-96231b3b80d8