[MEDIUM] http: revert to use a swap buffer for realignment

[MEDIUM] http: revert to use a swap buffer for realignment

The bounce realign function was algorithmically good but as expected
it was not cache-friendly. Using it with large requests caused so many
cache thrashing that the function itself could drain 70% of the total
CPU time for only 0.5% of the calls !

Revert back to a standard memcpy() using a specially allocated swap
buffer. We're now back to 2M req/s on pipelined requests.