support frame subtitles

beamerfontthemelcsb-base.sty

@@ -5,7 +5,7 @@
 \setbeamerfont{section number}{size=\Huge}
 \setbeamerfont{block title}{size=\normalsize, series=\bfseries}
 \setbeamerfont{block title alerted}{size=\normalsize, series=\bfseries}
-\setbeamerfont*{subtitle}{size=\large}
+\setbeamerfont{framesubtitle}{size=\footnotesize, series=\normalfont}
 \setbeamerfont{frametitle}{size=\large, series=\bfseries}
 \setbeamerfont{caption}{size=\small}
 \setbeamerfont{caption name}{series=\bfseries}

beamerouterthemelcsb.sty

@@ -4,7 +4,10 @@
   \begin{tikzpicture}
   \node[anchor=north west, text width=\paperwidth-12mm, minimum height=24pt] (thetitle) at (6mm,0) {
     \insertframetitle
-    \ifx\insertframesubtitle\@empty\else\par\normalfont\insertframesubtitle\fi
+    \ifx\insertframesubtitle\@empty\else\par\begingroup%
+      \usebeamercolor[fg]{framesubtitle}\usebeamerfont{framesubtitle}\par%
+      \insertframesubtitle%
+    \endgroup\fi
   };
   \iflcsb@standout
     \path (0,0);%alignment dummy