Antonio Ospite authored Oct 23, 2018 and Federico Mena Quintero committed Oct 23, 2018

The RsvgDimensionData structure uses pixels as unit for drawing
dimensions (see librsvg/rsvg.h), but the default unit for SVG documents
in cairo is pt; thus, when exporting to SVG with rsvg-convert, the
output drawing results scaled up compared to the original one.

Since rsvg already converted input units to pixels, it's safe to assume
the SVG output is always in pixels, so set the SVG surface units to
pixels to keep the original dimensions.

Bump cairo dependency to 1.5.12 as cairo_svg_surface_set_document_unit()
was not available before that version.

Fixes #365