Silence some more gcc fallthrough warnings (no real issues)

Author: nyalldawson

src/app/main.cpp

@@ -384,6 +384,7 @@ void myMessageOutput( QtMsgType type, const char *msg )
       dumpBacktrace( 256 );
       abort();                    // deliberately dump core
 #endif
+      break; // silence warnings
     }
 
 #if QT_VERSION >= 0x050500

src/providers/postgres/qgspostgresexpressioncompiler.cpp

@@ -191,6 +191,7 @@ QgsSqlExpressionCompiler::Result QgsPostgresExpressionCompiler::compileNode( con
         return Complete;
       }
 #endif
+      FALLTHROUGH;
     }
 
     default: