Font lock module qualification differently

[gracjan]

Currently we can recognize tokens that are qualified by module path. For example:

Control.Monad.>>=
Data.List.sort
Data.Map.Map
Data.HList.:~:
Control.Category..

We have a regexp that knows about module prefix and the unqualified part. It means that we can highlight differently the parts:

1. The module names.
2. The dots that are module separators (last dot can be different if we care).
3. The unqualified identifier, constructor or symbol.

Note that we do good job of differentiating the dot operator even if it is qualified.

Note2: Unicode prettification composition could be built in in this mechanism so that it is done in the same pass.

[gracjan]

Related: #725.

[gracjan]

So the pull request highlight whole qualified name in the same way as unqualified name would be highlighted. Much less visual noise and I like it that way much better.