Org reader: ensure emphasis markup can be nested

Nested emphasis markup (e.g. `/*strong and emphasized*/`) was
interpreted incorrectly in that the inner markup was not recognized.

src/Text/Pandoc/Readers/Org/Inlines.hs

@@ -647,6 +647,9 @@ emphasisStart c = try $ do
   char c
   lookAhead (noneOf emphasisForbiddenBorderChars)
   pushToInlineCharStack c
+  -- nested inlines are allowed, so mark this position as one which might be
+  -- followed by another inline.
+  updateLastPreCharPos
   return c
 
 -- | Parses the closing character of emphasis

tests/Tests/Readers/Org.hs

@@ -47,6 +47,10 @@ tests =
           "/*strength*/" =?>
           para (emph . strong $ "strength")
 
+      , "Emphasized Strong preceded by space" =:
+          " */super/*" =?>
+          para (strong . emph $ "super")
+
       , "Strikeout" =:
           "+Kill Bill+" =?>
           para (strikeout . spcSep $ [ "Kill", "Bill" ])