In clients that support DiagnosticRelatedInformation, display
clang notes as these nested diagnostics rather than appending
them to the parent diagnostic's message. Behaviour for clients
that don't support related information should be unchanged.
Fix#190
If a new header is added, the preamble size changes. Language clients may cache completion results, thus we rebuild preamble to avoid inaccurate results.
* In the "initialized" callback, send client/registerCapability with DidChangeWatchedFilesRegistrationOptions
* In workspace/didChangeWatchedFiles callback, call pipeline::Index
* In pipeline::Index, add a `deleted` status
* 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.
