Ms writer: Super/subscript support.

Also added some macro definitions to default template
to support subscripts + better superscripts.

data/templates/default.ms

@@ -11,6 +11,16 @@ $if(has-inline-math)$
 delim ||
 .EN
 $endif$
+\" From https://lists.gnu.org/archive/html/groff/2012-07/msg00046.html
+\" Superscripts (ex tmac.e) (current versions without extra line space)
+.\" (reinstate commented versions to restore extra line space)
+.\" .ds { \v'-0.3m'\x'-0.2m'\\s[\\n[.s]*8u/10u]
+.ds { \v'-0.3m'\\s[\\n[.s]*9u/12u]
+.ds } \s0\v'0.3m'
+.\" Subscripts
+.\" .ds < \v'0.3m'\x'0.2m'\s[\\n[.s]*8u/10u]
+.ds < \v'0.3m'\s[\\n[.s]*9u/12u]
+.ds > \s0\v'-0.3m'
 $if(title)$
 .TL
 $title$

src/Text/Pandoc/Writers/Ms.hs

@@ -397,10 +397,10 @@ inlineToMs opts (Strikeout lst) = do
   return $ text "[STRIKEOUT:" <> contents <> char ']'
 inlineToMs opts (Superscript lst) = do
   contents <- inlineListToMs opts lst
-  return $ char '^' <> contents <> char '^'
+  return $ text "\\*{" <> contents <> text "\\*}"
 inlineToMs opts (Subscript lst) = do
   contents <- inlineListToMs opts lst
-  return $ char '~' <> contents <> char '~'
+  return $ text "\\*<" <> contents <> text "\\*>"
 inlineToMs opts (SmallCaps lst) = do
   -- see https://lists.gnu.org/archive/html/groff/2015-01/msg00016.html
   modify $ \st -> st{ stSmallCaps = not (stSmallCaps st) }