Bad codegen when casting procs

[yglukhov]

proc foo() {.importc.}
(cast[proc(a: int) {.cdecl.}](foo))(5)

Error: execution of an external compiler program 'clang -c  -w  -I/Users/yglukhov/Projects/nim/lib -o /Users/yglukhov/nimcache/test2.o /Users/yglukhov/nimcache/test2.c' failed with exit code: 1

/Users/yglukhov/nimcache/test2.c:94:6: error: too many arguments to function call, expected 0, have 1
        foo(((NI) 5));
        ~~~ ^~~~~~~~
/Users/yglukhov/nimcache/test2.c:13:11: note: 'foo' declared here
N_NIMCALL(void, foo)(void);
          ^
1 error generated.