All: remove unused FontAwesome utilities classes

* icon-muted
* icon-border
* icon-2x
* icon-3x
* icon-4x
* icon-spin

These appear to be unused, according to an org-wide search on GitHub,
excluding matches in repos that don't use jquery-wp-content for their
content (e.g. irc.jquery.org, bugs.jquery.com, and archived content
repos such as web-events).

Ref #455.

themes/jquery/css/base.css

@@ -694,12 +694,6 @@ a [class*=" icon-"] {
 .nav [class*=" icon-"].icon-large {
   line-height: .9em;
 }
-.btn [class^="icon-"].icon-spin,
-.nav [class^="icon-"].icon-spin,
-.btn [class*=" icon-"].icon-spin,
-.nav [class*=" icon-"].icon-spin {
-  display: inline-block;
-}
 .nav-tabs [class^="icon-"],
 .nav-pills [class^="icon-"],
 .nav-tabs [class*=" icon-"],
@@ -734,35 +728,6 @@ ul.icons li [class^="icon-"],
 ul.icons li [class*=" icon-"] {
   width: .75em;
 }
-.icon-muted {
-  color: #eee;
-}
-.icon-border {
-  border: solid 1px #eee;
-  padding: .2em .25em .15em;
-  border-radius: 3px;
-}
-.icon-2x {
-  font-size: 2em;
-}
-.icon-2x.icon-border {
-  border-width: 2px;
-  border-radius: 4px;
-}
-.icon-3x {
-  font-size: 3em;
-}
-.icon-3x.icon-border {
-  border-width: 3px;
-  border-radius: 5px;
-}
-.icon-4x {
-  font-size: 4em;
-}
-.icon-4x.icon-border {
-  border-width: 4px;
-  border-radius: 6px;
-}
 .pull-right {
   float: right;
 }
@@ -777,62 +742,10 @@ ul.icons li [class*=" icon-"] {
 [class*=" icon-"].pull-right {
   margin-left: .3em;
 }
-.btn [class^="icon-"].pull-left.icon-2x,
-.btn [class*=" icon-"].pull-left.icon-2x,
-.btn [class^="icon-"].pull-right.icon-2x,
-.btn [class*=" icon-"].pull-right.icon-2x {
-  margin-top: .18em;
-}
-.btn [class^="icon-"].icon-spin.icon-large,
-.btn [class*=" icon-"].icon-spin.icon-large {
-  line-height: .8em;
-}
-.btn.btn-small [class^="icon-"].pull-left.icon-2x,
-.btn.btn-small [class*=" icon-"].pull-left.icon-2x,
-.btn.btn-small [class^="icon-"].pull-right.icon-2x,
-.btn.btn-small [class*=" icon-"].pull-right.icon-2x {
-  margin-top: .25em;
-}
 .btn.btn-large [class^="icon-"],
 .btn.btn-large [class*=" icon-"] {
   margin-top: 0;
 }
-.btn.btn-large [class^="icon-"].pull-left.icon-2x,
-.btn.btn-large [class*=" icon-"].pull-left.icon-2x,
-.btn.btn-large [class^="icon-"].pull-right.icon-2x,
-.btn.btn-large [class*=" icon-"].pull-right.icon-2x {
-  margin-top: .05em;
-}
-.btn.btn-large [class^="icon-"].pull-left.icon-2x,
-.btn.btn-large [class*=" icon-"].pull-left.icon-2x {
-  margin-right: .2em;
-}
-.btn.btn-large [class^="icon-"].pull-right.icon-2x,
-.btn.btn-large [class*=" icon-"].pull-right.icon-2x {
-  margin-left: .2em;
-}
-.icon-spin {
-  display: inline-block;
-  animation: spin 2s infinite linear;
-}
-@keyframes spin {
-  0% { transform: rotate(0deg); }
-  100% { transform: rotate(359deg); }
-}
-@-moz-document url-prefix() {
-  .icon-spin {
-    height: .9em;
-  }
-  .btn .icon-spin {
-    height: auto;
-  }
-  .icon-spin.icon-large {
-    height: 1.25em;
-  }
-  .btn .icon-spin.icon-large {
-    height: .75em;
-  }
-}
 /*  Font Awesome uses the Unicode Private Use Area (PUA) to ensure screen
     readers do not read off random characters that represent icons */
 .icon-glass:before                { content: "\f000"; }