fix fallthough comments for GCC 7.x

GCC 7.x does some extended checks on fallthough for switch/case
statement. The warning looks like this:

warning: this statement may fall through [-Wimplicit-fallthrough=]

It can be told about implicit fallthough, however it does not
recognize comments within blocks, so move the comments outside.

ColumnsPanel.c

@@ -65,8 +65,8 @@ static HandlerResult ColumnsPanel_eventHandler(Panel* super, int ch) {
          if (!this->moving) {
             break;
          }
-         /* else fallthrough */
       }
+         /* else fallthrough */
       case KEY_F(7):
       case '[':
       case '-':
@@ -81,8 +81,8 @@ static HandlerResult ColumnsPanel_eventHandler(Panel* super, int ch) {
          if (!this->moving) {
             break;
          }
-         /* else fallthrough */
       }
+         /* else fallthrough */
       case KEY_F(8):
       case ']':
       case '+':

MetersPanel.c

@@ -128,8 +128,8 @@ static HandlerResult MetersPanel_eventHandler(Panel* super, int ch) {
          if (!this->moving) {
             break;
          }
-         /* else fallthrough */
       }
+         /* else fallthrough */
       case KEY_F(7):
       case '[':
       case '-':
@@ -144,8 +144,8 @@ static HandlerResult MetersPanel_eventHandler(Panel* super, int ch) {
          if (!this->moving) {
             break;
          }
-         /* else fallthrough */
       }
+         /* else fallthrough */
       case KEY_F(8):
       case ']':
       case '+':