Bug#884850: librsvg: test failures on 32-bit no longer FTBFS

[Simon McVittie]

Control: severity 884849 normal
Control: severity 884850 normal
Control: retitle 884849 librsvg: test failure on any-i386: masking-path-04-b.svg: 213 pixels differ (with maximum difference of 19) from reference image
Control: retitle 884850 librsvg: test failure on (32-bit && !any-i386): masking-mask-01-b.svg: 661 pixels differ (with maximum difference of 2) from reference image

I've marked both these tests to be skipped during the build on 32-bit
architectures. If autopkgtests are added at some point, they'll still
be run there. The differences between the reference image and the actual
output are still bugs, but don't seem release-critical.

These tests were new in 2.40.19, so they've never passed on the affected
architectures in Debian - this is probably a pre-existing bug being
demonstrated by new test coverage, rather than a regression.

    smcv