Move using below #include to make preamble happy
textDocument/references: if no references, first line or last line => list where this file is included
malloc_trim() only if files have been indexed in last cycle
Intern: use CachedHashStringRef
Before, QueryFile::Def::{all_symbols,outline} were built by indexers.
Now, {symbol,outline}2refcnt are used instead, built by main thread.
*_removed are augmented with Query*:Def to allow removal of old {symbol,outline}2refcnt entries.
