minirst: create valid output when table data contains a newline

When table data contained a newline, the result of minirst.maketable
did not look nice plus it was not recognised by minirst.format:
  == === ====
  l1 1   one
  l2 2   2
22
  l3
  == === ====

This problem occurred when the description of options had a very long
translation which was split by newlines. Do not bother a translator with
this detail.

The multiline translations for option descriptions have been fixed in
baf1600adfbe in it.po, de.po and ro.po. I manually did the same as this patch
does, I removed the newlines.

When a newline was in the description, this created unusable help output:
  $ hg help somecommand
  hg somecommand [option]...

  with somecommand, you can...

  options:

  == =================== =======================================================
  =================================== --longdesc VALUE    xxxxxxxxxxxxxxxxxxxxxx
  xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx -n --norm
  normal desc --newline VALUE line1 line2 == =================== ===============
  ===========================================================================

now this looks much nicer:
  ...
  options:

      --longdesc VALUE xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                       xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
   -n --norm           normal desc
      --newline VALUE  line1 line2
doc: gendoc.py creates valid output for option descriptions with newlines

gendoc.py did not handle the hanging indentation for descriptions. Work around
this by joining all in one single line (same as in minirst since previous
patch).

This problem occurred when translations of option lines were very long. Do not
bother the translators with this detail.

On a long option description, the translator continued on a new line as usual.
gendoc.py created invalid rst syntax like this:

-o, --option
    Description line 1
description line 2

The new output is:

-o, --option
    Description line 1 description line 2

The lines could theoretically become very long, but line breaking is handled
when generating the final documentation.
setdiscovery: document algorithms used

This is taken from:
http://programmers.stackexchange.com/questions/208998
And modified slightly.
revset: added order methods to lazyset classes

This will allow revsets to ask for an ordered set when possible to be able to
work lazily with it.
revset: added sort method to orderedlazyset
revset: changed methods in spanset to return ordered sets

Now __sub__ and __and__ can smartly return ordered lazysets.