Better support for pasting text with tabs

[Wiktor Walc]

Problem: when pasting text with a tab, tab is changed into one space in IE (or space surrounded by <span> in Safari).

Sometimes users are using tabs to indent text. After creating text in notepad (for example), they copy that text into the editor... and notice the problem that text is not anymore indented as they expected it to be (tab is not shown as 4 spaces or something like that).

Instead of changing tabs automatically into one space, we could change them into configurable number of spaces (in a similar way like it is possible to set editor.config.tabSpaces).

Steps to reproduce

• create the following text in notepad:

  Test<tab>Test
  Test<space><space><space><space>Test
  

  (where <tab> is simply a tab)
• copy and paste it in the editor
• result in IE8:

  <p>
  	Test&nbsp;Test<br />
  	Test&nbsp;&nbsp;&nbsp; Test</p>
  

  result in Safari 4.0.4:

  <p>
  	Test<span class="Apple-tab-span" style="white-space:pre"> </span>Test</p>
  <p>
  	Test &nbsp; &nbsp;Test</p>
  

[Garry Yao]

We will not be able to provide such a fix as those browsers steal tab character already before we can check it.

[Jakub Ś]

This issue was duplicated in #8500.

[Jakub Ś]

#8609 was marked as duplicate.