Bug 929513 - gfxIntSize -> IntSize in ipc/ directory

(Detail: Chose to put an #include for Point.h in a header instead of a
forward declaration because a fwd decl caused an "Already defined" error
and having neither fwd decl or #include caused another compile failure
saying IntSize was undefined)
Bug 929513 - gfxIntSize -> IntSize in ipc/Shadow* files
Bug 929513 - gfxIntSize -> IntSize for Texture* classes
Bug 929513 - gfxIntSize -> IntSize in ThebesLayer* classes
Bug 929513 - Change all remaining gfxIntSize -> IntSize refs