tests: add wl_global tests

Test if creating two globals with the same id and creating global
with wrong version failes.

Also test creating singletons. The code remained there although it is
not a bug, see comments in the code.
tests: unit tests for test-compositor
tests: add tests for tc-events from test-compositor
tests: add wl_registry tests

test global and global_remove events

One tests fails, see
http://lists.freedesktop.org/archives/wayland-devel/2013-October/011573.html
for more info.