Make InstalledUnitId be ONLY a FastString.

It turns out that we don't really need to be able to
extract a ComponentId from UnitId, except in one case.
So compress UnitId into a single FastString.

The one case where we do need the ComponentId is when
we are compiling an instantiated version of a package;
we need the ComponentId to look up the indefinite
version of this package from the database.  So now we
just pass it in as an argument -this-component-id.

Also: ghc-pkg now no longer will unregister a package if
you register one with the same package name, if the
instantiations don't match.

Cabal submodule update which tracks the same data type
change.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

1 files changed, 0 insertions, 0 deletions

diff --git a/libraries/Cabal b/libraries/Cabal
-Subproject 8fa4d2ea2be385e715a10c77d6381d78e1421f7
+Subproject 579fd676a6f066775dcce9427c8463d0dbae101