Fix test for compilers not supporting \u escapes in strings (such as VC6).

Fix test for compilers not supporting \u escapes in strings (such as VC6).

Also reformat the code to follow wx style and explicitly use UTF-8 for the
test strings encoding instead of assuming the encoding of the current locale
was UTF-8 (which is never the case under Windows).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@63685 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775