[Bug c/82354] semi-colon instead of comma in parameter list produces confusing diagnostics

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82354

--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Note: the pertinent extension appears to be documented here:
https://gcc.gnu.org/onlinedocs/gcc-7.2.0/gcc/Variable-Length.html#index-parameter-forward-declaration

(see @cindex parameter forward declaration within extend.texi)