Persian accidentals look ugly

[Kees van den Doel]

> I'm not top posting.

Persian accidentals (korn, sori) don't look very nice. Solution: add koron and
sori to feta font, define accidentals.koron and accidentals.sori and modify
header file persian.ly by uncommenting/commenting some lines.

To run the code sample below download persian.ly and font MicroTxt.pfb
from here: http://www.cs.ubc.ca/~kvdoel/tmp/persian.zip

\version "2.12.2"
\include "persian.ly"
\paper{ ragged-right=##t } 
\score {
  \relative c' {
    \time 7/8
    \set Staff.extraNatural = ##f
    \set Staff.keySignature = \chahargahD
    \override Score.KeySignature #'text = #chahargahDKey
    bk'8[ a gs] fo4  g8[ ak] g[ fs ek] d[ c] d[ ef16 d] c4
    \set Staff.keySignature = \mokhalefsegahG
    \override Score.KeySignature #'text = #mokhalefsegahGKey
    \times 2/3 {d8 ek fo} g16 fo g4 
  }
  \midi { }
  \layout { }
}