STY: Boolean values for bint variables
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Looks fine.  Any reason to suspect a performance impact?  (for this one id look at the generated C code and see if it suddenly became more verbose) > Looks fine. Any reason to suspect a performance impact? (for this one id look at the generated C code and see if it suddenly became more verbose)

I looked a the generated C-code, there is no difference (except for the comments that show the equivalent code at the ```pyx``` file), this change is purely a stylistic change. > I looked a the generated C-code, there is no difference (except for the comments that show the equivalent code at the `pyx` file), this change is purely a stylistic change.

Can you run benchmarks to be sure?  > > I looked a the generated C-code, there is no difference (except for the comments that show the equivalent code at the `pyx` file), this change is purely a stylistic change.
> 
> Can you run benchmarks to be sure?

Sure!
@WillAyd Can you please guide to which asv benchmarks you'd like to see for this PR? also you can run `cython -a` to generate the annotate code to see if there is any difference (alt just recompile); if the c-code is the same then we are good.  > also you can run `cython -a` to generate the annotate code to see if there is any difference (alt just recompile); if the c-code is the same then we are good.

@jreback I have done both, and the result are the same.

---

I also did a small POC, what I did was:

Created  a file called ```foo.pyx``` and it's contents:

```cython
def f(bint VAR_NAME=0):
    pass
```

then ran:

```bash
cython -3 foo.pyx
mv foo.c foo_ZERO.c   # So future diff won't have diffs related to the file name.
rm -f foo.*                     # Was afraid that cython uses same file name as cache or something crazy like that
```

then I rewrote ```foo.pyx```, and it's contents:

```cython
def f(bint VAR_NAME=False):
    pass
```

and then I ran:

```bash
cython -3 foo.pyx
mv foo.c foo_FALSE.c
```

and then I checked via ```vimdiff```:

```bash
vimdiff foo_ZERO.c foo_FALSE.c
```

![generated_c_code](https://user-images.githubusercontent.com/50263213/77597561-ebd0b800-6f07-11ea-990d-afbe9cc227cc.png)

---

I have also included the two files generated in the POC

[foo.zip](https://github.com/pandas-dev/pandas/files/4384372/foo.zip)

 Thanks!