Add stream_await() for async stream "blocking"

Summary: As with cURL, use stream_await() to drop the fd
into the asio event loop and get notified of read/write events.

Reviewed By: @JoelMarcey

Differential Revision: D1720052

Signature: t1:1720052:1418353349:c7c252f30e901d40e303e3e445ddf518aaf98d6d
Adjust Is DSO Extension test check

Summary: We now look for if we can traverse ../../hphp/test/run back to ourselves instead.  This fixes a false positive when you have a ../hhvm folder outside of your DSO extension folder.

Also fixes some style issues.

This is a replacement pull for facebook/hhvm#4419.
Closes https://github.com/facebook/hhvm/pull/4432

Reviewed By: @JoelMarcey

Differential Revision: D1735988

Signature: t1:1735988:1418419042:7d763df76767be6beb80c1eba343da6f2543e58a
Adding lexer error to HPHP output

Summary: output lexer error to HPHP

Initial code review to validate approach.

Reviewed By: @paroski

Differential Revision: D1708518

Signature: t1:1708518:1418418481:862ce03615400f9ed2cd05022e8cbfc7931aac81