Gets the specialized type if possible from
NameNode.analyse_as_type

This does introduce a potential new bug:
```
cimport cython

just_float = cython.fused_type(float)

cdef OK1(just_float x):
    return just_float in floating

cdef fail1(just_float x, floating y):
    return just_float in floating

cdef fail2(floating x):
    return floating in floating

def show():
    """
    >>> show()
    True
    True
    True
    True
    """
    print(OK1(1.0))
    print(fail1(1.0, 2.0))
    print(fail1[float, double](1.0, 2.0))
    print(fail2[float](1.0))
```
fail1 and fail2 work before this patch but fail with it. It isn't
clear to me if this should actually be considered a bug. It
works in both versions with `cython.floating`, which possibly
suggests analyse_as_type in AttributeNode should also be changed