This gives quickfix/location lists created by handlers which use
'response_to_list' (textDocument/documentSymbols and workspace/symbol by
default) the ability to set a more useful list title. This commit gives
lists created for documentSymbols a title of the form:
Symbols in <filename>
and lists for workspace/symbol a title of the form:
Symbols matching '<query>'
These are more informative than a standard "Language Server" list title
and can help disambiguate results when users have multiple quickfix
lists that they cycle through with `:colder` and `:cnewer`.
574a582202
