Input group sizes: Properly position `.form-control-feedback`

Ref https://github.com/twbs/bootstrap/issues/12868#issuecomment-76291513
Ref 7733f243

less/forms.less

@@ -144,7 +144,7 @@ output {
     background-color: @input-bg-disabled;
     opacity: 1; // iOS fix for unreadable disabled content; see https://github.com/twbs/bootstrap/issues/11655
   }
-  
+
   &[disabled],
   fieldset[disabled] & {
     cursor: @cursor-disabled;
@@ -376,12 +376,14 @@ input[type="checkbox"] {
   text-align: center;
   pointer-events: none;
 }
-.input-lg + .form-control-feedback {
+.input-lg + .form-control-feedback,
+.input-group-lg + .form-control-feedback {
   width: @input-height-large;
   height: @input-height-large;
   line-height: @input-height-large;
 }
-.input-sm + .form-control-feedback {
+.input-sm + .form-control-feedback,
+.input-group-sm + .form-control-feedback {
   width: @input-height-small;
   height: @input-height-small;
   line-height: @input-height-small;