Since the introduction of "ColumnLimit: 120" in .clang-format, the
column limit has become 120 characters instead of 80 characters.
This prevents clang-format from generating too much changes even if just
a small portion of a source file or header file is modified.
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.
* 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.
