Update to SVG_use()

+ If $src is not a URL, make it one
+ Set xmlns:xlink & version attributes on <svg>
+ New function SVG_use_URI (URL encoded SVG_use)
Revert test case

Only send notification of __FILE__ & __LINE__
Fix enforce directive

Use true instead of "1"
Submodule classes/core 9fb7094..575e82a:

> Merge branch 'master' of github.com:shgysk8zer0/core
> Merge to apply updates
> New methods stepUp/Down and mark functions as final
JavaScript methods for json_response stepUp/Down methods

Need to apply these methods to progress, meter, etc