#3684: reset width to auto for input type='image'

docs/assets/css/bootstrap.css

@@ -873,6 +873,7 @@ input[type="checkbox"] {
   cursor: pointer;
 }
 
+input[type="image"],
 input[type="submit"],
 input[type="reset"],
 input[type="button"],

less/forms.less

@@ -139,7 +139,8 @@ input[type="checkbox"] {
   cursor: pointer;
 }
 
-// Reset width of input buttons, radios, checkboxes
+// Reset width of input images, buttons, radios, checkboxes
+input[type="image"],
 input[type="submit"],
 input[type="reset"],
 input[type="button"],