Update fontconfig submodule for https://github.com/mozilla-servo/fontconfig/pull/1

This of course depends on https://github.com/mozilla-servo/fontconfig/pull/1 being merged.
fix visibility warnings in main crate (#2044)
fix visibility warnings in script crate (#2044)
Make box_ not Option in block flows.(fixes #2012)
Introduce a set_uint_attribute method.
Remove some more xray code.
Implement Document.createElementNS.
Remove trailing whitespace.
auto merge of #2055 : Ms2ger/servo/trws, r=jdm

Done with `git ls-tree --name-only -r HEAD . | grep "\.rs" | xargs sed -i 's/\s\+$//g'`
Handle an exception from cx.evaluate_script more gracefully.
auto merge of #2057 : Ms2ger/servo/evaluate_script, r=jdm
auto merge of #2053 : Ms2ger/servo/createElementNS, r=jdm

#1391 rebased
auto merge of #2048 : Ms2ger/servo/set_uint_attribute, r=jdm
auto merge of #2051 : Ms2ger/servo/more-xray, r=jdm

On top of #2050
Add reftest for setAttribute restyling
Make sure getElementById always returns the first element with the given ID in tree order.(fixes #1822)
auto merge of #2062 : j3parker/servo/issue346-reftest, r=jdm

ref-test for #346
Move Node.namespaceURI to Element.(fixes #2059)
Remove all traces of C wrappers for SpiderMonkey class stubs.
auto merge of #2040 : SimonSapin/servo/fontconfig-compile, r=jdm

This of course depends on https://github.com/mozilla-servo/fontconfig/pull/1 being merged.