The Apache Maven Compiler (MC) API only allows a single source file extension, such as '.java'.
The AspectJ Compiler (AJC) should consider two default extensions, though: '.java' and '.aj'.
In order to achieve that, the Plexus AJC component tells MC to give it all files,
subsequently filtering for those two extensions.

The purpose of this file is to make sure that even though MC finds it in the source folder,
Plexus AJC filters it out and AJC does not try to compile it. 
