Bug 959058 - Map GBK and GB2312 decoder constructors to the GB18030 decoder. r=emk.
Additional test for bug 959058 - Check that 0x80 still decodes as euro on pages labeled as gbk. r=emk.

--HG--
rename : intl/uconv/tests/test_bug959058.html => intl/uconv/tests/test_bug959058-1.html
rename : intl/uconv/tests/test_bug959058.html => intl/uconv/tests/test_bug959058-2.html