Unreviewed GTK gardening.

Adding failure expectations for the two reftests added in r145982, failing due to disabled subpixel layout.
Triaging/enhancing failure expectations for spellcheck tests after r145940.

* platform/gtk/TestExpectations:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146022 268f45cc-cd09-0410-ab3c-d52691b4dbfc