lang/ghc: Update to 8.6.3 and bump PORTREVISION's of all Haskell ports.

As usual, it is recommended to rebuild or reinstall all the
dependent ports and the lang/ghc port itself in one of the following
ways:

1. portmaster -w -r ghc or
2. portupgrade -fr lang/ghc

In case of pkg(8), it is probably safer to remove all the GHC-dependent
packages along with GHC and reinstall everything from scratch. For
example:

1. pkg query "%ro" ghc > ghc-pkgs.txt
2. pkg delete -y lang/ghc
3. pkg install -y cat ghc-pkgs.txt

During update some hs-* ports got two PORTREVISION bumps in a row. Other ports
got a PORTVERSION update together with one PORTREVISION bump. This is caused
by bulk-bumping PORTREVISION of all hs-* ports. There are a lot of them updated,
so figuring out which ones require a bump and which are not is too tedious.

Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D18707