After trying a bit, i found out that the problem had something to do with my linux distribution. Now it compiles fine with AGC and i can confirm that AGC works fine, at least as good as in the Official/Original Firmware. Finally, no more switching to the OF because of AGC and manually compressing the WAV files to MP3, when i'm recording/archiving lectures. It now works on the fly in Rockbox. Thanks for your support and thanks for developing Rockbox!