[test] Latex special characters: Add failing and incomplete tests

test/test_songbook/latex_special.yaml

@@ -0,0 +1,14 @@
+book:
+  datadir:
+  - latex_special_datadir
+
+template:
+  default.tex:
+    title: "TODO"
+    author: "TODO"
+  patacrep.tex:
+    subtitle: "TODO"
+    url: "TODO"
+    email: "TODO"
+    picture: "img/treble_a"
+

test/test_songbook/latex_special_datadir/songs/special.csg

@@ -0,0 +1,8 @@
+{title : & % $ # _ } { ~ ^ \ }
+{by: & % $ # _ } { ~ ^ \ }
+
+& % $ # _ } { ~ ^ \
+
+{soc}
+  & % $ # _ } { ~ ^ \
+{eoc}