HHVM: Add static.mime-types.hdf

I'm not sure if this is still required by HHVM, but our current configuration
file does reference it, so make sure it is made available.

I obtained the file from
<https://raw.githubusercontent.com/mtorromeo/archlinux-packages/master/hhvm/static.mime-types.hdf>.

Change-Id: I3c1d12e29d9693ee0609a1e7eb38761107c5d4ef