Correctly output a single char_type

On platforms where char_type is typedef'd to an integral type
rather than to wchar_t, when using the insertion operator <<
a single char_type is output as the number corresponding to the
code point of the character rather than as the character itself.
In this case, one has to use put().

(cherry picked from commit 144f06a00c)

src/CutAndPaste.cpp

@@ -171,7 +171,7 @@ pasteSelectionHelper(DocIterator const & cur, ParagraphList const & parlist,
 				char_type const c = insertion[i].getChar(j);
 				if (!e->encodable(c)) {
 					// do not track deletion
-					res << c;
+					res.put(c);
 					insertion[i].eraseChar(j, false);
 					--end;
 					--j;