Fix a reference leak

Remove errant assert

Pluck some low hanging concurrency fruit

Fix a TSAN reported race

Make the shutdown flag on servers be per thread to save contention on
the lock that must guard it.

close() could race with epoll_ctl(); pretend to be polling while adding
to the epoll set to prevent this

Add .pc file generation to Makefile

Tweak timeouts for ?SAN

Fix a bug in the multipoll on poll path where we use a file descripto…

Fix iomgr shutdown TSAN races

Try harder to return DEADLINE_EXCEEDED when we should

Prevents TSAN races in iomgr shutdown code

Prevents a race whereby we start deleting the freelist before it's used

Do this by ensuring that the alarm callback has had a chance to run on a
call before returning status to the application.

If we do not do this:
- the server alarm could be scheduled and run
- it will write a RST_STREAM with a status that loses the deadline
  exceededness (because that is unexpressable in HTTP2 error codes)
- it will be received by the client and processed
- the client will return an INTERNAL error (the lossy re-encoding of the
  server status), and then run its alarm handler to set the status to
  something else

Eliminate data-race caused by specialization in vector<bool>

Base64 decode improvements

Memory leak fix

Fix fd handling on posix

Fix leak in chttp2_transport.c

Remove the ability to specify a cancellation string