BUG/TST: fix several issues with slice bound checking code
This patch removes more of what's left after removing pandas-specific customizations to slice indexing.

BUG/TST: `obj.iloc[:,-4:-10]` should return empty slice (because slice.step > 0 and slice.start > slice.stop)
There's no way to describe this by setting stop to a value in  `[0; len]` interval, it should remain negative (see [this ticket in python bugtracker](http://bugs.python.org/issue11842)]. Proposed fix to this issue is to remove the custom logic altogether. A side-effect of that is correct handling of negative steps in presence of out-of-bounds slices, e.g. `obj.iloc[:,10:4:-1]` would've incorrectly returned empty slice.

BUG: fix exception raised by `Series([1,2,3]).iloc[10:]`.
After I've cleaned up suspicious code that handled empty-sequence keys in #6440, this piece of code started causing trouble:

``` python
if start >= l:
    return self._getitem_axis(tuple(),axis=axis)
```

CLN: #6299 & #6443 rendered `core.indexing._check_slice_bounds` function useless and it's now gone.  Next step would be to drop unused `raise_on_error` parameter in slice-related functions.

Not sure, how do I put down all these relations into changelog, advice on that is welcome.

you can drop the raise_on_error parameter as it was just something to 'fix' the slicing issues (from somewhere in 0.12-0.13 transition).

Just put this all in a single line in API changes (its not really an API change, but more prominent), list all of the related issues.
 > Just put this all in a single line in API changes (its not really an API change, but more prominent), list all of the related issues.

Did I get you correctly: https://github.com/immerrr/pandas/commit/c7e634596b32df9151710a9cb43a0813c5a307d1#diff-5a809a5e093be4fe1396cbadd5bbeccaR110 ?
 tep
 yep
 Ok, folding/rebasing it then.
 minor change

I think you can move _slice from frame/panel to generic (but series still overrides)
 Whoops, apparently I've accidentally deleted wrong gh branch when cleaning up local ones, sorry about that.
 Also, `_slice` is now in ndarray as requested.
 can you rebase on currentmaster and push again.thxs
 Ok, done.
 thanks as always!

if you are interestdd #6536
 Sure, that was a low hanging fruit :)
