Java's Arrays.sort more robust and is faster is certain cases.

See #3919 and
https://github.com/sri/jruby-sort-benchmark.

* This (conservatively) ensures that even if the very first instruction
  of the BB might raise an exception, the rescue block sees state from
  entry of the BB, rather than (optimistically) from the end of the BB
  which control might never reach.

* The conservative assumption also matches the JVM verifier's assumption
  and should ensure that generated bytecode passes the verifier

* Verified that the generated IR is correct on the following snippet.
--------
def foo
  saved = bar()
ensure
  bar(saved)
end
--------

Use Java's Arrays.sort

to differentiate between a single object which happens to be an
array vs an array which happens to represent a set of values we
want to call eqq on.  The discriminator in IRBuilder is whether
we see Args{Cat,Push}Node or SplatNode (at least for when
statements...it is possible we need this for rescue_eqq too?).

…om somewhere else rather than installing.

returning :wait_readable instead of raising when op would block

+ hide method (receiving a buffer param) used internaly

…ith GraalVM.

# Conflicts:
#	.travis.yml