Remove [ConvertToString] from CodeGeneratorCPP.pm and rename

Remove [ConvertToString] from CodeGeneratorCPP.pm and rename
it to [ObjCImplementedAsUnsignedLong]
https://bugs.webkit.org/show_bug.cgi?id=78100

Reviewed by Eric Seidel.

Now [ConvertToString] is used by ObjC's HTMLElement.size only.
This patch removes [ConvertToString] code from CodeGeneratorCPP.pm,
and renames [ConvertToString] to [ObjCImplementedAsUnsignedLong].

No tests. No change in behavior.

* bindings/scripts/CodeGeneratorCPP.pm:
(GenerateImplementation):
* bindings/scripts/CodeGeneratorObjC.pm:
(GenerateImplementation):
* html/HTMLInputElement.idl: Removed FIXME comment, because the latest spec
says HTMLInputElement.size should be unsigned long.
(http://www.whatwg.org/specs/web-apps/current-work/multipage/the-input-element.html#the-input-element)

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107148 268f45cc-cd09-0410-ab3c-d52691b4dbfc