Improve a layout LYXERR0 message

The name of the layout is now included in an error message about
layouts. This will help with finding the root issue of several
documents we have.

(cherry picked from commit c949268da7)

src/output_latex.cpp

@@ -1189,8 +1189,9 @@ void latexParagraphs(Buffer const & buf,
 		if (layout.intitle) {
 			if (already_title) {
 				LYXERR0("Error in latexParagraphs: You"
-					" should not mix title layouts"
-					" with normal ones.");
+					" are using a layout (\"" << layout.name() << "\")"
+					" intended for the title, after using"
+					" non-title layouts.");
 			} else if (!was_title) {
 				was_title = true;
 				if (tclass.titletype() == TITLE_ENVIRONMENT) {