… it.

This reverts commit 25a735a.

See my notes at #3352.

In Ruby 2.2+, we have #receiver, so it makes sense to use consistent names
here and and get rid of #self and #self= in favor of #receiver and #receiver=

These were lost by accident while resolving merge conflicts between the master
branch and the 2.2 branch.

This commit fixes a build error due to a signature mismatch of the Time::at
method and the way it was being used in Stat::stat_birthtime.

The implementation relies on Module#direct_superclass to run through the
whole ancestry chain as #superclass would not include the modules.

The method is about 2 times slower than the MRI implementation though.
Benchmark: http://git.io/vmhpf.

Based on commit ruby/ruby@b4981594.

Interesting enough MRI still lets you define methods on these objects
even when they're frozen. For example, this works just fine:

    def nil.foo
    end

    nil.foo

* master:
  Fixes to assist building Rubinius under Alpine Linux (with musl).
  Changed "of the issue" to "if the issue"
  Contributing notes on version managers/releases
  Expand $PID in Metrics filename.
  Clean up log output of serial_debug/ic_debug
  Specify `superclass` in respect to `prepend`
  Fix correction to documentation for OnStack class.
  Fixed typ in the OnStack class
  Log class names for invalid ivars_ references
  Add a C-API "rb_hash_clear"
  Fix Range#bsearch for matching end value in find-minimum mode
  Fix String#split with 0 limit. Fixes #3474
  Add a String#split spec with 0 limit

Convert a fd to -(fd + 1) if its a Fixnum seems wrong.
Negative fds's are mostly invalid.

* 2.2:
  allow nil,true,false to be modified when frozen

Check for st_atim, st_mtim, st_ctim, etc. in struct stat (sys/stat.h)