add absolute alias for abs (#36597)
Summary:
Adds an absolute alias for the abs function to match Numpy's use of both:
https://docs.scipy.org/doc/numpy/reference/generated/numpy.absolute.html
Adds test to ensure the output from abs and absolute are the same.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36597
Differential Revision: D21024458
Pulled By: jessebrizzi
fbshipit-source-id: 4f2987e7bc7cde444d0a93e833a0350844b48d44
