guile 1.6 conversion

[Doug Evans <dje@transmeta.com>]

The biggest task in converting to guile 1.6 is handling the
stricter type checking on string operations.

(string-append "a" 'b)

is ok in guile 1.[34], but not guile 1.6.

It's not portable scheme so we shouldn't do that anyway,
but the simplicity of less stringent type checking in this
particular situation is compelling.

We could go through all of cgen and insert the appropriate
conversions (symbol->string, etc.) but while it may the a correct
thing to do, it's rather cumbersome and the result isn't easy to maintain.

I propose a different solution.
[No claim is made that these are the only solutions.
Other solutions are easily dreamt up at the speed of thought. :-)]

Let's keep the notion of being able to freely pass symbols to
a "string-append"-like function, but just give it a different name
like strsym-append or some such.
There a handful of other functions involved but you get the idea.