Support for a_call + a_return Ruby events

Koichi patched these in as a "hidden feature" during a talk on `TracePoint` during RubyConf 2013; the idea being that `a_call` is an umbrella for `call`, `b_call`, and `c_call`, and the same for `a_return`. Add support for these in JRuby.

The MRI commit for is [here for reference](https://github.com/ruby/ruby/commit/ac778eb2cf8f66a7c15573a73c620f237f9f17dd).

I realize this implementation doesn't seem to be very clean, but I don't think building in something as clean as the MRI's will be possible without some large refactoring. I also considered just adding a conditional in the event listener, but I would guess that this would be inferior performance-wise.

I added a test to the suite where most of the `TracePoint` tests seem to be kept, but realized later that all of these seem to be [currently excluded](https://github.com/jruby/jruby/blob/master/test/mri/excludes/TestSetTraceFunc.rb#L1). Perhaps if someone could give me some backstory here, I could try to look into this as well.