Add other profile tools:

  * dump_gcov: Dump the afdo file.
  * sample_merger: Merge two perf.data files into a text format.
  * profile_merger: Merge two afdo files.
  * profile_diff: Diff two afdo files.
  * profile_update: Update the afdo file with the new compilation info in binary.
Merge pull request #3 from google/more_tools

Add other profile tools: