[API] Issues with TSHttpHdrVersionGet

[SUSAN HINRICHS <sh...@apache.org>]

The TSHttpHdrVersionGet API returns the HTTP version set in the header
object referenced by the bufp and obj arguments.  For HTTP/1.0 and HTTP/1.1
requests, this works as you would expect.  For HTTP/2, this will return
HTTP/1.1 because HTTP/2 stream requests get translated to HTTP/1.1 requests
from the HttpSM perspective.

int

TSHttpHdrVersionGet(TSMBuffer bufp, TSMLoc obj)

We could update the HttpSM logic to explicitly set the HTTPHdr to HTTP/2
(or h2) for requests from HTTP/2 streams.  This will require a thorough
review of the HttpSM code since there are places that explicitly check the
version number and would skip unknown versions.

We could update TSHttpHdrVersionGet to dig through the protocol stack and
return HTTP/2 anyway.  The response back to the client will say HTTP/2 in
any case.

We could leave it all as is and update the documentation to reflect current
behavior (just stub documentation at the moment).  Perhaps point the reader
to the ProtocolStack APIs for those who want to know the real version.

Any thoughts?