Fix up last few alias tests in core

[Earlopain]

And also one for zlib.

Previously I just checked core/*/shared.
But some didn't use that, and others I skipped by accident.

I used the following script (with --disable-gems) to find aliased methods:

require "objspace"

r = {}
ObjectSpace.each_object(Module) do |mod|
  next if mod.inspect.include?("<Object:")
  methods = mod.public_instance_methods.map { mod.instance_method(it) }
  methods += mod.public_methods.map { mod.method(it) }
  methods.each do |meth|
    to_find = methods.select { it.name != meth.name }
    next if to_find.none? { it == meth }
    next if meth.owner != (meth.is_a?(Method) ? mod.singleton_class : mod )
    r[mod] ||= []
    r[mod] << meth
  end
end

r = r.transform_values do |methods|
  methods.group_by(&:itself).values
end

pp r

Closes #1364

[eregon]

Thank you!