sample guile-2.0 extension in manual

[Johan Hidding]

Hi,
In manual chapter 5.3.1 there is a small example program. Using GCC 4.6,
this only compiles with -fpermissive, unless an explicit
reinterpret_cast<scm_t_subr> (which is an alias for (void *)) is used.
Should this be considered a (minor) bug in the manual?
Cheers, Johan