Fixes #5167 and related problems (#5475)

This commit returns to a bit less strict checking of the number
of macro arguments, because some old immediate macros rely on a
behavior where even the arity of the macro is not being checked.

It may be better if such macros are just declared to use varargs[expr],
but this remains for another day.

compiler/ast.nim

@@ -460,6 +460,8 @@ type
                       # proc foo(T: typedesc, list: seq[T]): var T
                       # proc foo(L: static[int]): array[L, int]
                       # can be attached to ranges to indicate that the range
+                      # can be attached to generic procs with free standing
+                      # type parameters: e.g. proc foo[T]()
                       # depends on unresolved static params.
     tfRetType,        # marks return types in proc (used to detect type classes
                       # used as return types for return type inference)