The bitmap allocation data structure prototypes. Before
this is released these underlying data structures need
to be more performant but the signatures of helper
functions utilizing these structures will remain stable.

Change-Id: I5ace12f2fb512a7038a52bbde2bfb7e98783bcbe
Reviewed-on: https://go-review.googlesource.com/19221Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>