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.
Move all the generated code for enums into CGEnum.
Remove EnumEntry, as Rust already provides O(1) access to the string length.
Use ToJSValConvertible to convert enums to JSVal.
Use ToJSValConvertible to convert nullable enums to JSVal.
Remove XRay related stuff from codegen (fixes #1936)
Remove some more xray code.
Implement Document.createElementNS.
Remove trailing whitespace.
Handle an exception from cx.evaluate_script more gracefully.
HTMLImageElement attribute getters and setters
Add reftest for setAttribute restyling
Make sure getElementById always returns the first element with the given ID in tree order.(fixes #1822)
Move Node.namespaceURI to Element.(fixes #2059)
Remove all traces of C wrappers for SpiderMonkey class stubs.
Split out a do_set_attribute method.