Hi!

I've developed the following patch, which fixes R5RS-compatibility for
printing symbols starting/ending with ':'. The problem with the
current behaviour is that you end-up with files that can not be read
from other Schemes when you write out such symbols:

guile> (write ':foo) (newline)
#{:foo}#
guile>

My patch changes this behaviour to what you'd expect:

guile> (write ':foo) (newline)
:foo
guile>

However, when the keywords reader option is set, the old behaviour is
re-established, to allow writing out these symbols in "escaped form"
so that they can be read back when the prefix keywords reader option
is turned on.