Revert a gratuitous change

This commit reverts a change made at 3bc08a76 that was causing
changed output. See:
http://www.mail-archive.com/lyx-devel@lists.lyx.org/msg200509.html

src/output_latex.cpp

@@ -1153,7 +1153,7 @@ void TeXOnePar(Buffer const & buf,
 			// prevent unwanted whitespace
 			os << '%';
 		if (!os.afterParbreak() && !last_was_separator)
-			os << breakln;
+			os << '\n';
 	}
 
 	// if this is a CJK-paragraph and the next isn't, close CJK