Move protectArgument function to lstrings

This will be useful to other insets as well.

src/insets/InsetCitation.cpp

@@ -312,15 +312,6 @@ inline docstring wrapCitation(docstring const & key,
 			html::htmlize(content, XHTMLStream::ESCAPE_ALL) + "</a>";
 }
 
-docstring protectArgument(docstring & arg, char const l = '[',
-			  char const r = ']')
-{
-	if (contains(arg, l) || contains(arg, r))
-		// protect brackets
-		arg = '{' + arg + '}';
-	return arg;
-}
-
 } // anonymous namespace
 
 

src/support/lstrings.cpp

@@ -1203,6 +1203,16 @@ docstring const escape(docstring const & lab)
 }
 
 
+docstring const protectArgument(docstring & arg, char const l,
+			  char const r)
+{
+	if (contains(arg, l) || contains(arg, r))
+		// protect brackets
+		arg = '{' + arg + '}';
+	return arg;
+}
+
+
 bool truncateWithEllipsis(docstring & str, size_t const len)
 {
 	if (str.size() <= len)

src/support/lstrings.h

@@ -269,6 +269,10 @@ docstring const rsplit(docstring const & a, char_type delim);
 /// problems in latex labels.
 docstring const escape(docstring const & lab);
 
+/// Group contents of an argument if needed
+docstring const protectArgument(docstring & arg, char const l = '[',
+			  char const r = ']');
+
 /// Truncates a string with an ellipsis at the end.  Leaves str unchanged and
 /// returns false if it is shorter than len. Otherwise resizes str to len, with
 /// U+2026 HORIZONTAL ELLIPSIS at the end, and returns true.