Non-ASCII characters fail to display correctly on many systems (when using Imagemagick)

both Drupal and Imagemagick's convert tool are standardized on working with UTF-8 as only encoding. However, sending texts to the Imagemagick convert tool without having any of the intermediate tools/systems (escapeshellarg(), proc_open(), the shell in use, the operating system) mangle it is not easy and error-prone.

The current implementation of the text effect does work on some systems, but fails on quite some others.

Solution:
Rewrite the Imagemagick specific part by letting it place the text to show in a temporary file and pass that with the @ operator to the Convert tool. On hook_exit(), these temporary files should be removed.

Bonus:
Passing multi-line texts now becomes easier and will be supported from now on. Note: this is not the samne as automatic text wrapping or fitting.