get rid of one more ccomp constraint

don't generate packed structs with long long fields, e.g.:
$ cat foo.c
struct {
  long long f2;
} a[1] = {0};
$ ccomp -fall c foo.c
foo.c:2: Error: Initializer is not a compile-time constant (undefined binary operation)

Bad failure message?
Merge branch 'master' of github.com:csmith-project/csmith