[CM] C Stack Unwinding

[bil at ccrma.Stanford.EDU]

Argh -- this is two problems.  First the documentation
is incomplete or incorrect (depending on whether you've
had lunch), and has been for a long time -- s7_define_function
returns the function name as a symbol, whereas s7_make_function
returns the function.  The comment in s7.h is also wrong.
Sorry about that!  The second bug is that you didn't get
an error when the catch process tried to apply the symbol
to the error info arguments.  I don't know why not yet.
If you turn on S7_DEBUGGING, you'd get a complaint
about trying to apply a symbol.