fix run.php notice

spews on first run

Reviewed By: @JoelMarcey

Differential Revision: D1150540
switch X-Powered-By to HHVM/1.0.0

This is a little clowny since we've completly rebranded.

Reviewed By: @scannell

Differential Revision: D1149784
Add missing consts to intl extension

Can't know what bits to use if you
don't know what ICU you're on.

Reviewed By: @JoelMarcey

Differential Revision: D1132218
Enable FCallBuiltin for HNI functions

Design around HNI and treat IDL as the special case.

Reviewed By: @ptarjan

Differential Revision: D1147229