Switched from line-height to text-indent to accessibly hide buttons. Fixes jquery-archive#1927

Was causing an vertical scroll bar to appear in FF9 if a button at the
end of the content div is disabled / enabled. Changed '''line-height:
999px''' to '''text-indent: -9999px'''. Thanks n0v1!

Author: toddparker

css/structure/jquery.mobile.button.css

@@ -47,4 +47,4 @@
 .ui-bar .ui-btn-icon-bottom .ui-icon { bottom: 4px; }
 
 /*hiding native button,inputs */
-.ui-btn-hidden { position: absolute; top: 0; left: 0; width: 100%; height: 100%; -webkit-appearance: button; opacity: .1; cursor: pointer; background: #fff; background: rgba(255,255,255,0); filter: Alpha(Opacity=.0001); font-size: 1px; border: none; line-height: 999px; }
+.ui-btn-hidden { position: absolute; top: 0; left: 0; width: 100%; height: 100%; -webkit-appearance: button; opacity: .1; cursor: pointer; background: #fff; background: rgba(255,255,255,0); filter: Alpha(Opacity=.0001); font-size: 1px; border: none; text-indent: -9999px; }