Change c++_codegen_lib from build: protoc to build: all

fixes to tests for py2/3 syntax compatibility

Don't check read_info for writes

Adding an argument to bad_ssl_cert in order to override the location of the test certificate.

PHP: remove hardcoded version in templates

Fix Node status code usage to match spec

Revert for good "Pass a non-infinite deadline to grpc_completion_queue_next() to prevent queues from blocking indefinitely in poll()"

DocFixit: Troubleshooting info for Windows and some minor tweaks

Fix copyright for metrics.proto

Fix failure handling code

Fix some issues in building under certain configurations

Python 3: fix a bytes/str runtime issue

Specification for stress test clients

Add HTTP request parsing

Fix timeout decoding logic for times that become infinite

python 2/3 compatible abstract servicers/stubs

Python: py3 compatibility for test runner & loader

Make a copy of ByteBuffer when writing

Reorder asserts to avoid TSAN failure

Make unix sockets optional

Make grpc-python ByteBuffer.bytes() linear

This extends the existing http parser to support requests as well as responses.

httpcli continues to exist and work as it has previously, though in the new
directory src/core/http (to reflect the fact the directory now contains code
relevant to parsing requests, which httpcli would not generally involve itself
in).

On python3, in grpc._links.service._Kernel._on_service_acceptance_event,
there is a runtime TypeError:

```
_on_service_acceptance_event
    group, method = service_acceptance.method.split('/')[1:3]
TypeError: 'str' does not support the buffer interface
```

It is fixed by using a bytes literal (`b'/'`) instead of a string literal.

This exposed another issue in grpc.beta._server where an exception was being
raised with a bytes literal for a message (a string should be used instead.)