Fix auto wrapping of text with explict newlines

Previous changes to avoid including whitespace in width calculations
accidentally broke layout if the text contained intentional newlines.
They were previously handled correctly implicitly, before the change to
trim unnecessary whitespace, which now requires explicitness.

Fixes: 2b3b873 ("Improve AutoWrappingText trimming")

Fixes #878

src/customcontrols.cpp

@@ -129,6 +129,11 @@ wxString WrapTextAtWidth(const wxString& text_, int width, Language lang, wxWind
         else if (pos > 0 && text[pos-1] == '\n') // forced line feed
         {
             out += substr;
+            out += '\n';
+#ifdef BIDI_NEEDS_DIRECTION_ON_EACH_LINE
+            if (directionMark)
+                out += directionMark;
+#endif
             lineStart = pos;
             previousSubstr.clear();
         }