test-compositor: add tc-events.[ch]

This is support for simulating events. It will be used by
test-compositor.
test-compositor: add libtc-server library

Server side functions
test-compositor: add client-side functions

Add functions which can be used by client's subprocess. The header has
been already added.
test-compositor: add main header file

Add test-compositor header file
tests: look even for test-compositor headers

Search for headers in test-compositor/ dir
test-compositor: add README
autotools: link against test-compositor libraries

Tests using test-compositor need to be linked against it
tests: add wl_shm test

The test uses test-compositor