Rename async_execution_lock --> combiner, make it use closures, unroll previous changes for idleness

This reverts commit c9d4b81d.

Changed the README file of PHP example

Change cancelled to cancelled?

Return success status of grpc_byte_buffer_reader_init

App to manually test behavior under changing connectivity conditions

Added missing dependencies to grpc++_base

Fix TSAN failure in tcp_server (shown via qps_openloop_test)

Merge branch 'protobuf-submodule-update' of https://github.com/nicolasnoble/grpc into bb_reader_error

Ruby garbage collection fixes

removed unused version of status_code_enum.h

Initialize variables in surface/call.c