TST: Add tests for constants.

Test the values of np.pi, np.e, and np.euler_gamma to make sure
they are correct to relative tolerance 1e-15.
Merge pull request #2838 from charris/test-numpy-constants

TST: Add tests for constants.
Added support for AArch64 architecture

Signed-off-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Merge pull request #2901 from hrw/master

Add support for AArch64 architecture