Bug 781360 patch 3: Rename {nsIFrame,nsStyleContext,nsComputedDOMStyle}::GetStyle* to Style*, since they can never return null.  r=dholbert

Except for the changes in:
  layout/generic/nsIFrame.h (part)
  layout/style/nsComputedDOMStyle.h (all)
  layout/style/nsRuleNode.cpp (part)
  layout/style/nsStyleContext.cpp (part)
  layout/style/nsStyleContext.h (part)
(see patch 3b in the bug), this patch was written with the sed script:
s/\<GetStyle\(Font\|Color\|List\|Text\|Visibility\|Quotes\|UserInterface\|TableBorder\|SVG\|Background\|Position\|TextReset\|Display\|Content\|UIReset\|Table\|Margin\|Padding\|Border\|Outline\|XUL\|SVGReset\|Column\)\>/Style\1/g
Bug 781360 patch 4:  Remove the Get from nsStyleContext::GetStyleData and nsIFrame::GetStyleDataExternal, which never return null.  r=dholbert