Dropdown in panel header does not inherit its colors

Fix for issue #10627

less/mixins.less

@@ -396,6 +396,9 @@
     + .panel-collapse .panel-body {
       border-top-color: @border;
     }
+    & > .dropdown .caret {
+      border-color: @heading-text-color transparent;
+    }
   }
   & > .panel-footer {
     + .panel-collapse .panel-body {

less/panels.less

@@ -92,6 +92,9 @@
   padding: 10px 15px;
   border-bottom: 1px solid transparent;
   .border-top-radius(@panel-border-radius - 1);
+  & > .dropdown .dropdown-toggle {
+    color: inherit;
+  }
 }
 
 // Within heading, strip any `h*` tag of it's default margins for spacing.