Added Polish translation
build: make distcheck pass.
NEWS file update.
RELEASING file update.
Post-release version bump.
Updated Polish translation
tests: an additional test file and more reference images.
svg: add a transformable class for object with 'transform' attribute.

It fixes a crash when 'transform' attribute is set on gradient elements.
It also reduce the memory use.
tests: import test files from librsvg bugzilla.
tests: more test file from librsvg bugzilla.
tests: more librsvg bugzilla files.
tests: more librsvg bugzilla files.
tests: add more librsvg bugzilla files.
tests: directory layout tweak.
svg: handle nodes with name prefixed with 'svg:'
svg: start of vertical text support.
mathml: support for element prefixed by 'math:'
mathml: fix update of itex element.

An update request on the itex element now forces an update of the
embededd math element, as the style may have changed.
mathml:itex: don't force measure on update if not needed.
mathml: document lsm_mathml_element_update.