fix parsing of GOOG128 type (len>=26)

Hi
Google user identifier seen at the moment on AdEx are 27 char. 
I am not sure about potential side effects of this --  here's what Jeremy said when discussing the topic on Skype:

"there are some implications for us internally to change it, as it changes the value of hash() and we have files serialized with those hashes"

But I don't  see why, since the hash should be computed on the internal 128 bits. 

Cheers