Comment 8 for bug 636021

REASON FOR ERROR (thanks to jwilk from pdf2djvu):

1.3.8 (January 21, 2010)
========================
[…]
Behavior Changes:

  * InitializeMagick() MUST be invoked prior to using any Magick API
    function. Failure to do so will likely lead to an immediate
    application crash. This is due to initialization and runtime
    changes intended to improve thread safety and efficiency.
    Previously it was only strongly recommended to invoke
    InitializeMagick().

SOLUTION:

In source file "main.cc" add the following line before the first while in the function (maybe there is a better place, but this one works):

InitializeMagick(NULL);

Solved semaphore.c:525 error :)