Guile 2 status

[Geert Janssens]

With r23444 I have squashed the last failing tests I ran into with 
guile 2 and auto-compilation enabled.

I am aware that our tests don't cover the full source code, so there 
may still be guile 2 related bugs lurking in some dark forgotten 
corners.

Nevertheless I consider the guile 2 support to be complete now.

Would this be a good time to start preferring guile 2 over guile 1.8 
when both are available ? It's an easy switch in configure.

Geert