[PATCH]: Doc: NR @knownissue for partCombine + spanners (issue4629073)

[pkx166h]

Reviewers: ,

Message:
To address

http://code.google.com/p/lilypond/issues/detail?id=1643

I realise this is slightly more than the above issue asks for :) but I
hope you like the edits and it improves this section.

I certainly learnt some 'stuff'.

James

Description:
Doc: NR  @knownissue for partCombine + spanners

Consolidtated some of the existing @knownissues so they aren't just a
long
unreadable list. Took the opportunity to tidy up the syntax and correct
some of the
examples as per the CG.

Added an @seealso that references back to autobeaming where another
@knownissue for \partcombining is referred to.

Please review this at http://codereview.appspot.com/4629073/

Affected files:
  M Documentation/notation/simultaneous.itely