Baseline: c645a452

Cherry picks:
   + af878d04: Add coverage support for java test. (series 4/4 of
              open-sourcing coverage command for java test)
   + 09b92a8f: Rollback of commit
              67b4d525.
   + b11dd482: Fix bad bug with the parallel implementation of
              BinaryOperatorExpression. Turns out that
              ForkJoinTask#adapt(Callable) returns a ForkJoinTask
              whose Future#get on error throws a ExecutionException
              wrapping a RuntimeException wrapping the thrown checked
              exception from the callable. This is documented
              behavior [1] that I incorrectly didn't know about.
   + 9012bf16: Fix scripts/packages/convert_changelog to read the
              changelog correctly
   + 55c97bcf: Release script: if master branch does not exist, fall
              back on origin/master
   + 4fb378c0: Debian repository: override section and priority fields
   + acbcbc2f: Fix release notes in emails
   + 49757602: Fix PathFragment to not use Java8-only static hashCode
              methods.
   + 05fd076b: Disable sandboxing for XibCompile actions.

Incompatible changes:

  - Skylark maven_jar and maven_aar settings attribute is now a label
    so it can be checked into your workspace.
  - --{no}experimental_use_rclass_generator is now a nop.

New features:

  - Coverage support (*experimental*) for pure Java target.
    Use `bazel coverage //my:target` to generate coverage information
    from a `java_test`.

Important changes:

  - Enable fallback URLs in Skylark http rules.
  - cc_proto_library generates C++ code from proto_library rules.
  - cc_library now supports the strip_prefix and strip_include_prefix
    attributes for control of include paths.
  - Skylark dicts internally don't rely on keys order anymore and
    accept any hashable values (i.e. structs with immutable values)
    as keys. Iteration order of dictionaries is no longer specified.