allow non mixed use declarations, CC @nikic #1005

allow non mixed use declarations, CC @nikic #1005

```
use function N\S { foo, bar, etc };
use const N\S { FOO, BAR, ETC };
```

Related tests:

```
make test -j4 TESTS="-m Zend/tests/ns_0{88..92}*.phpt"
```

All namespace tests:

```
make test -j4 TESTS="Zend/tests/ns_*.phpt"
```