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 reference:

    https://github.com/ruby/ruby/commit/ac778eb2cf8f66a7c15573a73c620f237f9f17dd
Remove unneeded commenting
Turns out these tests are from Ruby Core; don't modify them
Reset test files according to master
Move A_CALL + A_RETURN to the end of the enum for binary compatibility

According to review comments.
Merge pull request #1217 from brandur/brandur-a-call-and-a-return

Support for a_call + a_return Ruby events