fixes #4852: popover carets fully functional in ie8 holy carp wtfbqq huge shoutout to @PumaOmaR

docs/assets/css/bootstrap.css

@@ -3812,6 +3812,7 @@ button.close {
   margin-left: -10px;
   border-top-color: #ffffff;
   border-bottom-width: 0;
+  content: " ";
 }
 
 .popover.right .arrow {
@@ -3828,6 +3829,7 @@ button.close {
   left: 1px;
   border-right-color: #ffffff;
   border-left-width: 0;
+  content: " ";
 }
 
 .popover.bottom .arrow {
@@ -3844,6 +3846,7 @@ button.close {
   margin-left: -10px;
   border-bottom-color: #ffffff;
   border-top-width: 0;
+  content: " ";
 }
 
 .popover.left .arrow {
@@ -3860,6 +3863,7 @@ button.close {
   bottom: -10px;
   border-left-color: #ffffff;
   border-right-width: 0;
+  content: " ";
 }
 
 .alert {

less/popovers.less

@@ -76,6 +76,7 @@
     border-top-color: @popover-arrow-outer-color;
     bottom: -@popover-arrow-outer-width;
     &:after {
+      content: " ";
       bottom: 1px;
       margin-left: -@popover-arrow-width;
       border-bottom-width: 0;
@@ -90,6 +91,7 @@
     border-right-color: #999; // IE8 fallback
     border-right-color: @popover-arrow-outer-color;
     &:after {
+      content: " ";
       left: 1px;
       bottom: -@popover-arrow-width;
       border-left-width: 0;
@@ -104,6 +106,7 @@
     border-bottom-color: @popover-arrow-outer-color;
     top: -@popover-arrow-outer-width;
     &:after {
+      content: " ";
       top: 1px;
       margin-left: -@popover-arrow-width;
       border-top-width: 0;
@@ -119,6 +122,7 @@
     border-left-color: #999; // IE8 fallback
     border-left-color: @popover-arrow-outer-color;
     &:after {
+      content: " ";
       right: 1px;
       border-right-width: 0;
       border-left-color: @popover-arrow-color;