Miscellaneous improvements to `Convert` (#1020)

Now that Haddock is moving towards working entirely over `.hi` and `.hie` files,
all declarations and types are going to be synthesized via the `Convert` module.
In preparation for this change, here are a bunch of fixes to this module:

  * Add kind annotations to type variables in `forall`'s whose kind is not `Type`,
    unless the kind can be inferred from some later use of the variable. See
    `implicitForAll` and `noKindTyVars` in particular if you wish to dive into this.

  * Properly detect `HsQualTy` in `synifyType`. This is done by following suit with
    what GHC's `toIfaceTypeX` does and checking the first argument of
    `FunTy{} :: Type` to see if it classified as a given/wanted in the typechecker
    (see `isPredTy`). 

  * Beef up the logic around figuring out when an explicit `forall` is needed. This
    includes: observing if any of the type variables will need kind signatures, if the
    inferred type variable order _without_ a forall will still match the one GHC
    claims, and some other small things.

  * Add some (not yet used) functionality for default levity polymorphic type
    signatures. This functionality similar to `fprint-explicit-runtime-reps`.

Couple other smaller fixes only worth mentioning:

  * Show the family result signature only when it isn't `Type`
  * Fix rendering of implicit parameters in the LaTeX and Hoogle backends
  * Better handling of the return kind of polykinded H98 data declarations
  * Class decls produced by `tyThingToLHsDecl` now contain associated type
    defaults and default method signatures when appropriate
  * Filter out more `forall`'s in pattern synonyms

1 files changed, 3 insertions, 11 deletions

diff --git a/html-test/ref/Instances.html b/html-test/ref/Instances.html
index 4f51f049..0cf0fc92 100644
--- a/html-test/ref/Instances.html
+++ b/html-test/ref/Instances.html
@@ -2038,8 +2038,6 @@
 			  >Int</a
 			  > c <a href="#" title="Data.Bool"
 			  >Bool</a
-			  > :: <a href="#" title="Data.Kind"
-			  >Type</a
 			  > <a href="#" class="selflink"
 			  >#</a
 			  ></p
@@ -2050,9 +2048,7 @@
 			  >Thud</a
 			  > <a href="#" title="Data.Int"
 			  >Int</a
-			  > c :: <a href="#" title="Data.Kind"
-			  >Type</a
-			  > <a href="#" class="selflink"
+			  > c <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -2112,9 +2108,7 @@
 			  >type</span
 			  > <a href="#" title="Instances"
 			  >Plugh</a
-			  > [a] c [b] :: <a href="#" title="Data.Kind"
-			  >Type</a
-			  > <a href="#" class="selflink"
+			  > [a] c [b] <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -2122,9 +2116,7 @@
 			  >data</span
 			  > <a href="#" title="Instances"
 			  >Thud</a
-			  > [a] c :: <a href="#" title="Data.Kind"
-			  >Type</a
-			  > <a href="#" class="selflink"
+			  > [a] c <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div