[gentoo-java] Detection of useless dependencies

[Petteri Räty]

If you are using JAVA_PKG_STRICT and install dev-java/java-dep-check, 
you will start to see messages like the following:
 >>> Merging dev-java/xstream-1.2-r2 to /
  * Possibly unneeded dependencies found in package.env:
  *      commons-cli-1

This means that xstream is recording a dependency on commons-cli-1 to 
package.env but the class files installed by xstream don't reference any 
classes from commons-cli in the constant pool. For most packages this 
means that you just remove the usage from the ebuild but the tool will 
also give you false positives if the dependency is only needed at 
runtime and is loaded a provider framework for example. These false 
positives will eventually be hidden by mandating the use of 
java-pkg_register-dependency for these dependencies and then we can use 
the values given to that function to filter those out from the results 
of java-dep-check.

Regards,
Petteri