[show-hint addon] Fix scrollbar on hint widget overlapping text

See https://discuss.codemirror.net/t/width-of-sql-hint-dropdown-in-firefox-is-not-always-correct/757

Author: marijnh

addon/hint/show-hint.css

@@ -26,7 +26,6 @@
   padding: 0 4px;
   border-radius: 2px;
   max-width: 19em;
-  overflow: hidden;
   white-space: pre;
   color: black;
   cursor: pointer;

addon/hint/show-hint.js

@@ -229,6 +229,7 @@
     var winH = window.innerHeight || Math.max(document.body.offsetHeight, document.documentElement.offsetHeight);
     (completion.options.container || document.body).appendChild(hints);
     var box = hints.getBoundingClientRect(), overlapY = box.bottom - winH;
+    var scrolls = hints.scrollHeight > hints.clientHeight + 1
     if (overlapY > 0) {
       var height = box.bottom - box.top, curTop = pos.top - (pos.bottom - box.top);
       if (curTop - height > 0) { // Fits above cursor
@@ -253,6 +254,7 @@
       }
       hints.style.left = (left = pos.left - overlapX) + "px";
     }
+    if (scrolls) hints.style.paddingRight = cm.display.nativeBarWidth + "px"
 
     cm.addKeyMap(this.keyMap = buildKeyMap(completion, {
       moveFocus: function(n, avoidWrap) { widget.changeActive(widget.selectedHint + n, avoidWrap); },