Memprof/Bleakhouse-like extension for JRuby

A memprof-like feature for JRuby to debug memory leaks, by telling the amount of live objects grouped by file and line-number from where they were created in the code. Could be enabled by giving an argument like "--memory-profiling" to JRuby, since it would properly eat some performance.

In memprof-mode JRuby saves the file and line number from allocated objects in a hash with a counter. Possibly with a hook into "Class.new" or something on the Java-side? When an object is freed the counter counts down (could possibly be hacked by using weak references if this is not possible otherwise?).

When a static method like "JRuby::Memprof.stats" is called or the application ends, the contents of this hash should be printed. It should then tell the amount of live objects from which file and line-number to debug memory leaks in the Ruby-side of the source code.