Reviewed by Beth Dakin.

Add support for relative positioning to table cells.   Back out the code that hacked around the lack of support
for offsetLeft, and add new tests to demonstrate that relative positioning works.

Source/WebCore: 

* css/CSSStyleSelector.cpp:
(WebCore::CSSStyleSelector::adjustRenderStyle):
* rendering/RenderObject.cpp:
(WebCore::RenderObject::offsetParent):
* rendering/RenderObject.h:
(WebCore::RenderObject::isRelPositioned):
* rendering/RenderTableCell.h:
* rendering/style/RenderStyle.h:
* rendering/style/StyleRareNonInheritedData.cpp:
(WebCore::StyleRareNonInheritedData::StyleRareNonInheritedData):
(WebCore::StyleRareNonInheritedData::operator==):
* rendering/style/StyleRareNonInheritedData.h:

LayoutTests: 

* fast/table/relative-position-containment.html: Added.
* fast/table/relative-position-offsets.html: Added.
* fast/table/relative-position-stacking.html: Added.
* platform/mac/fast/table/overflowHidden-expected.txt:
* platform/mac/fast/table/relative-position-containment-expected.checksum: Added.
* platform/mac/fast/table/relative-position-containment-expected.png: Added.
* platform/mac/fast/table/relative-position-containment-expected.txt: Added.
* platform/mac/fast/table/relative-position-offsets-expected.checksum: Added.
* platform/mac/fast/table/relative-position-offsets-expected.png: Added.
* platform/mac/fast/table/relative-position-offsets-expected.txt: Added.
* platform/mac/fast/table/relative-position-stacking-expected.checksum: Added.
* platform/mac/fast/table/relative-position-stacking-expected.png: Added.
* platform/mac/fast/table/relative-position-stacking-expected.txt: Added.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@81049 268f45cc-cd09-0410-ab3c-d52691b4dbfc