debian/control: Make mongodb arch all, instead of arch-specific.

The package mongodb is only a metapackage intended to pull in other packages
and it has absolutely zero architecture-specific content.

Signed-off-by: Rogério Brito <rbrito@ime.usp.br>
debian/patches: Add preparation for kFreeBSD.
kfreebsd does not have tcmalloc
enable building packages on kfreebsd
debian/patches: Regenerate the patches from patch queue.

With this change, we are very close (completely ready?) to having mongodb
working on kFreeBSD (and, perhaps, even HURD in the not-so-distant future).
We *may* have to switch from v8 to spidermonkey, as a libv8 that is ported
to kFreeBSD is apparently only in experimental at the moment of this
writing.

Thanks: Pino Toscano and Jeff Epler
Closes: #703061