Preventing session.el messing up with geiser-doc--history

Session seems to be recovering the value of geiser-doc--history
badly (see issue #7 for @achitu's discoveries), and since it is, in
fact, not a good idea to save it anyway, we've added an eval-on-load
deregistering the variable from session's list.
NEWS update
Experiment setting history file coding system
Another not entirely satisfactory experiment with raw-text
Using session instead of session.el for you bytecompilers
A couple of byte-compilation warnings gone
Debug code removed
Real solution for the non-ascii-history problem

We were using a history entry separator including \0 that wasn't
writeable as an utf-8 file.  Changing the separator to \n}{\n allows
using UTF-8 characters in the REPL which are correctly read back.
Merge branch 'master' of git://github.com/jaor/geiser