Fix scratch list

[bruno-]

Hi, I'm using vim-snipmate that in turn 'leans' on this library. Specifically tlib#input#List function is used (and maybe others).

Anyway - I noticed tlib scratch buffer does not behave nicely. After it is used:

• alternate buffer is changed. C-^ does not work as it should, it jumps back to scratch buffer
• scratch buffer is not completely deleted. That can be seen with :ls! command after the buffer is used (even without 'going back' with C-^

This pull request addresses the above with:

• setlocal bufhidden=wipe - properly deletes buffer after it's used
• keepalt command preserves alternate file
• keepj does not mess jump list (C-o, C-i)

I learned about these from netrw plugin error message buffer which is very similar to scratch buffer.

Let me know what you think about the updates?

[tomtom]

I made the change to the value of bufhidden user configurable (see g:tlib_scratch_hidden). The default behaviour is still "hide", though. The rationale is that those buffers usually are reused frequently.

[bruno-]

I just checked and the main things: alternate buffer and jump list work on. Thank you!