Bug 844288 - Dual link libxul.so and libxul-unit.so and replace enable-gtest by enable-test r=ted,glandium

- Remove enable GTest
- Add a general target to create gtestxul
- Update mach target
- Run GTest from make check

--HG--
rename : gfx/2d/unittest/GTestMain.cpp => gfx/tests/gtest/TestMoz2D.cpp
rename : gfx/layers/TestTiledLayerBuffer.cpp => gfx/tests/gtest/TestTiledLayerBuffer.cpp
extra : rebase_source : 5b9be0892323195d4e24f11ae785f0663ff38fd0
no bug remove more probably useless calls to expectAssertions()
Bug 877501 - Generate pref check code for interfaces with [NoInterfaceObject, NavigatorProperty]. r=bz

--HG--
extra : rebase_source : 02b9028c3ab215df0378af109d2bcac15d28e9b4