[FlowSensitive] Fix warnings

This patch fixes:

  clang/lib/Analysis/FlowSensitive/HTMLLogger.cpp:376:22: error:
  comparison of integers of different signs: 'unsigned int' and
  'TokenInfo::(unnamed enum at
  clang/lib/Analysis/FlowSensitive/HTMLLogger.cpp:356:7)'
  [-Werror,-Wsign-compare]

  clang/lib/Analysis/FlowSensitive/HTMLLogger.cpp:385:23: error:
  comparison of integers of different signs: 'unsigned int' and
  'TokenInfo::(unnamed enum at
  clang/lib/Analysis/FlowSensitive/HTMLLogger.cpp:356:7)'
  [-Werror,-Wsign-compare]

etc