Restore Header Table and Static Table Indices

[Jeff Pinner <[e-mail]>]

As request by Mark, I propose that the current HPACK draft be changed
such that Sec. 2.3.3 Index Address Space reads,

"Indices between 1 and the length of the dynamic table (inclusive)
refer to elements in the dynamic table.

Indices strictly greater than the length of the dynamic table refer to
elements in the static table. The length of the dynamic table is
subtracted from the index into the static table."

with the associated diagram updated. This reverts the change made
between draft -08 and -09 in the change log, "Exchanged header and
static table positions."