Added placeholder for cpu_windows.c implementation

Add visual studio project to build dll libraries.

Fixing valgrind's codepath in run_tests.py.

Update grpc_java_base Dockerfile to proto3

Server server credentials

Adding call host (:authority header) check in the secure channel.

Added a performance test

Improving Visual Studio templates

Windows port of iomgr.

Have unary pollset check to see if the existing fd is orphaned

This avoids an unnecessary upgrade to multipoller if there was no
do_work called between an orphan and a subsequent add. Additionally, it
avoids the need for epoll based multipoller to check for this case in
its upgrade code by ensuring all existing fds are valid at upgrade time.

Add a wrapping of grpc_server_credentials.

Work towards removing some contention

Proto3 is now required for Java, so build it including the Java runtime
since it is not on Maven.

- Fixes #405.
- This change is not tested as it should (only end to end and no
  negative testing). Will do better when we have testing framework
  for filters.

Fix some tests