* Add %h for C header files (the suffix .h is considered a C header, not a C++ header)
* Add %hpp for C++ header files
* If .ccls exists, it provides full command line for files not specified by compile_commands.json (before, compile_commands.json was ignored)
* If the first line of .ccls is %compile_commands.json, it appends flags to compile_commands.json "arguments", instead of overriding.
Files not specified by compile_commands.json will not be added to folder.entries, but their command line can be inferred from other files.
Also fix `#include <` completion of -I flags for clang < 8
textDocument/{declaration,definition,typeDefinition} return either LocationLink[] or Location[]
Add an initialization option client.linkSupport . When it is false, ccls will return Location[] disregarding client's linkSupport.
`struct LocationLink` does not include originSelectionRange as it is wasteful.
* WorkingFiles::files : vector -> unordered_map
* Add timestamp to WorkingFile
* Rename "comp-preload" thread to "preamble"
* Rename CompletionManager to SemaManager as it is used by "diag" "comp" "preamble"
* Rename clang_complete.* to sema_manager.*
* Merge SemaManager::{preloads,sessions}
* Add initialization option session.maxNum
* In DiagnosticMain, if an included file was modified, cancel the DiagTask and create a PreambleTask instead. The task sets `from_diag` so as to trigger immediate DiagTask after the preamble is built.
It decreases Content-Length: from 32K to 25K for the following case:
#include <bits/stdc++.h>
int main() { std::| }
Also
* make results deterministic when completion text is empty
* sort by newText, label, filterText
