gnu: ghc-pandoc: Update to 2.7.3.

* gnu/packages/haskell-xyz.scm (ghc-pandoc): Update to 2.7.3.
[source]: Add patches to fix tests.
[arguments]: Remove '#:phases'.
[inputs]: Remove 'ghc-deepseq-generics', 'ghc-old-locale', and
'ghc-yaml'; add 'ghc-hslua-module-system', 'ghc-hsyaml', 'ghc-ipynb',
and 'ghc-unicode-transforms'.
[native-inputs]: Add 'ghc-tasty-lua'.
* gnu/packages/patches/ghc-pandoc-fix-html-tests.patch: New file.
* gnu/packages/patches/ghc-pandoc-fix-latex-test.patch: New file.
* gnu/local.mk: Add them.

gnu/packages/patches/ghc-pandoc-fix-latex-test.patch

@@ -0,0 +1,31 @@
+This patch is taken from upstream.  It fixes a LaTeX test that is broken due
+to using a Skylighting version greater than or equal to 0.8.1.1.
+
+From 2cd1c7b30f200d18f1f1bdef1671369e1ad303ed Mon Sep 17 00:00:00 2001
+From: John MacFarlane <jgm@berkeley.edu>
+Date: Thu, 13 Jun 2019 19:33:52 -0700
+Subject: [PATCH] Update test for skylighting 0.8.1.1.
+
+---
+ test/lhs-test.latex | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/test/lhs-test.latex b/test/lhs-test.latex
+index 0442db5ca..a456995a3 100644
+--- a/test/lhs-test.latex
++++ b/test/lhs-test.latex
+@@ -94,9 +94,9 @@ return a single value:
+ 
+ \begin{Shaded}
+ \begin{Highlighting}[]
+-\OtherTok{unsplit ::}\NormalTok{ (}\DataTypeTok{Arrow}\NormalTok{ a) }\OtherTok{=>}\NormalTok{ (b }\OtherTok{->}\NormalTok{ c }\OtherTok{->}\NormalTok{ d) }\OtherTok{->}\NormalTok{ a (b, c) d}
++\OtherTok{unsplit ::}\NormalTok{ (}\DataTypeTok{Arrow}\NormalTok{ a) }\OtherTok{=>}\NormalTok{ (b }\OtherTok{{-}>}\NormalTok{ c }\OtherTok{{-}>}\NormalTok{ d) }\OtherTok{{-}>}\NormalTok{ a (b, c) d}
+ \NormalTok{unsplit }\OtherTok{=}\NormalTok{ arr }\OperatorTok{.} \FunctionTok{uncurry}
+-          \CommentTok{-- arr (\textbackslash{}op (x,y) -> x `op` y)}
++          \CommentTok{{-}{-} arr (\textbackslash{}op (x,y) {-}> x \textasciigrave{}op\textasciigrave{} y)}
+ \end{Highlighting}
+ \end{Shaded}
+ 
+-- 
+2.23.0
+