Dns retry support

Reachability ObjC fix

Node: propagate read errors back down to core

Support for coreclr

Update PHP composer.json files

Add clang3.4 and 3.6 support to run_tests.py

Remove unnecessary safety-refs

Move C-layer call creation into GRPCChannel, so that it always acts on a
non-destroyed channel.

Listen for connectivity in the GRPCCall, and destroy the channel.

Fix race between send message and send initial metadata

Ruby: fix some synchronization code in server implementation

Fix C# artifacts compatibility

Don't set linetrace unless testing coverage

Fixes #5561

Fix other typo to match previous typo fix.

Doc Fixit: src/cpp/README need more information

Release GIL in queue __dealloc__

Merge release-0_13 into master

Fix memory leak: keep all resolver calls under the same lock

Fix memory leak if call is already cancelled

Fix comparison direction - fixes timer_list_test flakiness