Revert "Replace use of editor.pasteClipboard with executeCommand("cmd_paste")."

This reverts commit 7e8db4743b24368ba1784420e6cdf6b4838958df.

The commit breaks selection pasting in linux, so reverting.

common/content/editor.js

@@ -339,7 +339,7 @@ function Editor() //{{{
 
     mappings.add(myModes,
         ["<S-Insert>"], "Insert clipboard/selection",
-        function () { editor.executeCommand("cmd_paste"); });
+        function () { editor.pasteClipboard(); });
 
     mappings.add([modes.INSERT, modes.TEXTAREA, modes.COMPOSE],
         ["<C-i>"], "Edit text field with an external editor",
@@ -621,6 +621,25 @@ function Editor() //{{{
             return text.substring(getEditor().selectionStart, getEditor().selectionEnd);
         },
 
+        pasteClipboard: function ()
+        {
+            let elem = window.document.commandDispatcher.focusedElement;
+
+            if (elem.setSelectionRange && util.readFromClipboard())
+                // readFromClipboard would return 'undefined' if not checked
+                // dunno about .setSelectionRange
+            {
+                let rangeStart = elem.selectionStart; // caret position
+                let rangeEnd = elem.selectionEnd;
+                let tempStr1 = elem.value.substring(0, rangeStart);
+                let tempStr2 = util.readFromClipboard();
+                let tempStr3 = elem.value.substring(rangeEnd);
+                elem.value = tempStr1 + tempStr2 + tempStr3;
+                elem.selectionStart = rangeStart + tempStr2.length;
+                elem.selectionEnd = elem.selectionStart;
+            }
+        },
+
         // count is optional, defaults to 1
         executeCommand: function (cmd, count)
         {