Implement viewports and transforms

Closed in favour of !322 (merged) and !323 (merged)

This is an implementation of wp_viewporter and transforms

It's based on old patches by Jasper St. Pierre and the weston implementation.

In can be tested with:

• westons weston-scaler [-b|-d|-s|-n]
• weston-simple-damage --transform=[normal|90|180|270|flipped|flipped-90|...] --rotating-transform --use-viewporter [--use-damage-buffer] --scale=[1|2|3|...]
• the gstreamer gtk-wayland demo (https://github.com/swt2c/gst-wayland-gtk-demo)

Implements: #132 (closed)

weston-scaler [-b,-d,-s,-n], weston-simple-damage --use-viewporter --scale=3 and the gstreamer wayland demo