Convert-ly in 2.12

[Nick Payne]

After installing 2.12 (running on Windows Vista), I notice that when I run 
convert-ly against an old ly file, it changes the version in the file to 
2.11.66:

D:\Documents\Lilypond>convert-ly -e mutopia\adelita.ly
convert-ly.py (GNU LilyPond) 2.12.0
Processing `mutopia\adelita.ly'...
Applying conversion: 2.9.4, 2.9.6, 2.9.9, 2.9.11, 2.9.13, 2.9.16, 2.9.19, 2.10.0
, 2.11.2, 2.11.5, 2.11.6, 2.11.10, 2.11.11, 2.11.13, Not smart enough to convert
 edge-text settings for TextSpanner.Use

        \override TextSpanner #'bound-details #'right #'text = <right-text>
        \override TextSpanner #'bound-details #'left #'text = <left-text>
2.11.15, 2.11.23, 2.11.35, Not smart enough to convert all settings related to d
ashed lines.
Use \override ... #'style = #'line for solid lines and
        \override ... #'style = #'dashed-line for dashed lines.2.11.38, 2.11.46,
 2.11.48, 2.11.50, 2.11.51, 2.11.52, 2.11.53, 2.11.55, 2.11.57, 2.11.60, 2.11.61
, 2.11.62, 2.11.64, 2.11.66

Seeing that this is supposed to be the stable version, I think it should put 
the current version number in the file, and not the last development version 
after which there were no conversion changes needed.

Nick