Protocol Cache: Improved vary detection.
Version bumped to 5.5.69 by buildsystem.
Version bumped to 5.5.70 by buildsystem.
Protocol Cache: Assume that vary is supported by all.

This change is to avoid the vary header on User-Agent, which was
generated by the CookieJar.

Removes the workaround for MSIE 6 having broken support for vary.
Merge branch 'patches/vary' into 5.5

* patches/vary:
  Protocol Cache: Assume that vary is supported by all.
  Protocol Cache: Improved vary detection.
Version bumped to 5.5.71 by buildsystem.
Version bumped to 5.5.72 by buildsystem.