Update adblockpluscore dependency to include perceptual image hashing optimisation

Background

The perceptual image hashing snippet turns out to be slow on Firefox, see adblockpluscore#55. Ollie has made some improvements there, we'd like to include those as soon as possible. We need to update the adblockpluscore dependency to do that.

Included changes

• Fixed #55 - Do not use getters inside loops

What to change

• Update the adblockpluscore dependency to hg:34bc161ef26f git:27bf314

Hints for testers

Test if the perceptual image hashing snippet performs better on Firefox.