Make it more explicit that Key modifiers is a bit field
Small tweak
Add a split function that does not take an escape and returns StringViews

When an escape character is not present, split can just return sub
strings of the parameter, so we can avoid duplicating the original
string data.
Port more code to StringView instead of const String&
Refactor highlighters, use an interface with virtual methods
Close fd before notifiying buffer of modification when writing to file
Reread file timestamp at the moment the user choose to keep

The previous behaviour ended up asking twice for reloading if the
buffer was modified again after Kakoune had detected the first
change.
cpp.kak: highlight cast operators
minor code tweaks
Fix slow InternedString copy constructor
centralize bit operation support for enum used as flags
Fix tag command, using IFS is a *bad* idea
Do not lose history when reloading a buffer

Fixes #157
Get non completion clang output into a buffer when completing
Add virtual destructor to Highlighter