`explain void f(int *const)` incorrectly rejected as "syntax error"

[Quuxplusone]

cdecl> declare f as function (const int) returning void
void f(const int)
cdecl> explain void f(const int)
declare f as function (const int) returning void
cdecl> declare f as function (const pointer to int) returning void
void f(int * const )
cdecl> explain void f(int * const)
syntax error

Trailing (i.e. top-level) cv-qualifiers on function parameters aren't recognized in general. For example:

cdecl> explain void f(int const)
syntax error

Also notice the superfluous space in void f(int * const ); it would be nice to get rid of that.

This issue basically blocks #7.