Bug 921753 - Part 2: Move GraphicsFilters outside of gfxPattern.h so that we won't need to #include that header everywhere GraphicsFilter is needed; r=roc

This patch reduces the number of files that transitively #include
gfx/2d.h from 1582 to 1362.
Bug 921753 - Part 3: Avoid #including nsStyleStructInlines.h in nsHTMLReflowState.h; r=roc

This patch reduces the number of files that transitively #include
gfx/2d.h from 1362 to 1268.
Bug 921753 - Part 4: Move DrawMode outside of gfxFont.h so that we won't need to #include that header everywhere DrawMode is needed; r=roc

This patch reduces the number of files that transitively #include
gfx/2d.h from 1268 to 1208.