[varnishcache/varnish-cache] 616c1e: Speed up VSB_bcat()

[Federico G. Schwindt]

  Branch: refs/heads/master
  Home:   https://github.com/varnishcache/varnish-cache
  Commit: 616c1ee573e4e1a0b98918acaee75f3d7e681bf9
      https://github.com/varnishcache/varnish-cache/commit/616c1ee573e4e1a0b98918acaee75f3d7e681bf9
  Author: Federico G. Schwindt <fgsch at lodoss.net>
  Date:   2015-12-15 (Tue, 15 Dec 2015)

  Changed paths:
    M lib/libvarnish/vsb.c

  Log Message:
  -----------
  Speed up VSB_bcat()

Rather than copying one char at the time extend the buffer as needed and
use memcpy.