Please make the PDF output reproducible

Whilst working on the Reproducible Builds effort [0], we noticed that rsvg-convert does not create reproducible output.

This is because it calls cairo_pdf_surface_create_for_stream without setting a modification time, thus leading to the current date always being generated.

An alternative patch could use the creation time of the input file, but this would be misleading metadata when applied to the output - it was not created at the same time as the input.

This has also been filed in Debian [1].

[0] https://reproducible-builds.org/ [1] https://bugs.debian.org/890027

Signed-off-by: Chris Lamb chris@chris-lamb.co.uk