embedding: rename string_list internal function to string_list instead of string_map
embedding: cef_string_utf8_cmp()
embedding: replace transmutes with manual casts in cef_string_utf8_cmp()
auto merge of #3946 : zmike/servo/embedding-fixups, r=jdm

adds a missing string api function and renames an existing string_list function

r+ @larsbergstrom @jdm ?