auto merge of #3685 : Ms2ger/servo/doc-reflector, r=jdm

This field became unused in commit 99a36cbeb6077976861d94b7af16e9e57994a14d.
embedding: implement cef_string_utf16_cmp()
embedding: begin cef string_list api

cef_string_list_alloc()
embedding: cef_string_list_size()
embedding: cef_string_list_append()
embedding: cef_string_list_value()
embedding: cef_string_list_clear()
embedding: cef_string_list_free()
embedding: cef_string_list_copy()
auto merge of #3679 : zmike/servo/embedding-string_list, r=larsbergstrom

Implements the full cef_string_list API

r+ @larsbergstrom ?
added ErrorEvent WebIDL and errorevent.rs
Removed InitErrorEvent
trying to resolve trace error
moving init in constrictor
removed InitErrorEvent
initial implementation of workers done
set alignment
partially completed worker implementation which gets compiled
implementation of workers complete