fix a bug in {Proc, Symbol}#allocate where it would be triggered the crash

Result:
$ macirb
irb(main):001:0> Proc.allocate
zsh: segmentation fault  macirb

Expected:
$ irb
irb(main):001:0> Proc.allocate
TypeError: allocator undefined for ProcExpected:
update spec's tag
use MACRUBY_STATIC for rb_undef_alloc_func
fix a bug in `undef' which it could call undefined method if call it once

Test Code:
----
class Foo
  def meth
  end
end

obj = Foo.new
obj.meth

class Foo
  undef meth
end
p obj.meth

Result:
----
$ macruby test_undef.rb
nil

Expected:
----
ruby test_undef.rb
test_undef.rb:12:in `<main>': undefined method `meth' for #<Foo:0x007f8231935d18> (NoMethodError)
fix a bug in Module#remove_method which it could call undefined method if call it once

Test Code:
----
class Foo
  def meth
  end
end

obj = Foo.new
obj.meth

class Foo
  remove_method :meth
end
p obj.meth

Result:
----
$ macruby test_remove.rb
nil

Expected:
----
$ ruby test_remove.rb
test_remove.rb:12:in `<main>': undefined method `meth' for #<Foo:0x007fad558b9cc8> (NoMethodError)
update spec's tag
Update RubyGems to v1.8.25
Update copyright year to 2013
Merge remote-tracking branch 'timfall/patch-1'

* timfall/patch-1:
  Create uninstall.sh

This addresses GH-190
Remove obsoleted lib/objc_ext extensions

There are no project using these extensions on
Github (at the time of this commit), so it is a
safe gamble that nobody will miss them.

Half of the functionality given here is already
provided by BridgeSupport and the other half is
trivial for a user to add themselves if they
really want it.