Letting any character to be escaped is error prone as it looks like
\l could mean [:lower:] (as it used to with boost) when it only means
literal l.
Fix the haskell.kak file as well.
Fixes#1945
Commit 870d2d22d7 introduced a regression
in the highlighting of qualified Haskell variables, such as `Foo.bar`.
After that commit `Fo` was highlighted as a constructor (note, not
`Foo`, just `Fo` without the trailing `o`). This restores the original
behavior.
That means we can now have highlighters active at global, buffer, and
window scope. The add-highlighter and remove-highlighter syntax changed
to take the parent path (scope/group/...) as a mandatory argument,
superseeding the previous -group switch.
boost regex tolerates non-escaped special characters, and escaped
non-special characters. Standardize on stricter syntax, where
special characters must be escaped, and non-special characters must
not.
Import keywords are put in keyword face instead of meta face.
This leaves room for pragmas and macros to be in the meta face.
Operator keywords are put in keyword face too.
Finally, expression keywords are put in face attribute.
The option is now used as a fallback when detection by extension fails. Some
scripts like `base/mail.kak` and `base/html.kak` still rely heavily on it.
