graphics/librsvg2: fix for locale bug in rsvg-convert

[Marcin Cieslak]

Hello,

rsvg-convert as released has an annoying bug:

Bug 557036 – rsvg-convert uses the wrong locale for command line processing

http://bugzilla.gnome.org/show_bug.cgi?id=557036

rsvg-convert refuses to work on UTF-8 filenames in the filesystem, 
regardless of the current locale.

Attached please find a simple patch to fix this.
Patch by Tim Starling of Wikimedia.

--Marcin