package/classpath: drop package

This package has been abandoned by upstream since 2016 and has not
had a release since 2012. In addition the GNU Compiler for Java
that classpath was written to be used with has been removed as of
GCC 7.

It is no longer feasible to support classpath as it requires a java
compiler capable of producing java 1.5 compatible bytecode which is
not possible on hosts with a recent java compiler.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>