Unreviewed, rebaseline several tests cases for GTK that have better results
after r147492.

* platform/gtk/TestExpectations:
* platform/gtk/fast/dom/HTMLImageElement/image-alt-text-expected.png:
* platform/gtk/fast/dom/HTMLImageElement/image-alt-text-expected.txt:
* platform/gtk/fast/dom/HTMLInputElement/input-image-alt-text-expected.png:
* platform/gtk/fast/dom/HTMLInputElement/input-image-alt-text-expected.txt:
* platform/gtk/fast/encoding/utf-16-big-endian-expected.png:
* platform/gtk/fast/encoding/utf-16-big-endian-expected.txt:
* platform/gtk/fast/encoding/utf-16-little-endian-expected.png:
* platform/gtk/fast/encoding/utf-16-little-endian-expected.txt:
* platform/gtk/fast/forms/input-value-expected.png:
* platform/gtk/fast/forms/input-value-expected.txt:
* platform/gtk/tables/mozilla/collapsing_borders/bug41262-3-expected.png:
* platform/gtk/tables/mozilla/collapsing_borders/bug41262-3-expected.txt:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147524 268f45cc-cd09-0410-ab3c-d52691b4dbfc