BUG: don't set a default for libraries configuration key

the get_libs function assumes there is no default to return the default
it was asked to return in that case.
Closes gh-4607
BUG: check if openblas embeds lapack

add openblas_lapack info which checks if it embedds lapack so
lapack_info will point to openblas
the normal openblas info does not check so it may or may not embed
lapack.
closes gh-4192
ENH: added functionality nanpercentile to numpy
Implemented a nanpercentile and associated tests
as an extension of np.percentile to complement the
other nanfunctions.
BUG: svd ufunc typo
Merge pull request #4735 from argriffing/fix-svd

BUG: svd ufunc typo
DOC: tweak gufunc API documentation, remove broken link.  Closes gh-4726.
Merge pull request #4738 from rgommers/gufuncs-doc

DOC: tweak gufunc API documentation, remove broken link.
Docs: fix numpy.fft.fft2 example

Fixes issue #4736

The example showed a call to np.fft.fft instead of np.fft.fft2.
Merge pull request #4739 from FRidh/docs

Docs: fix numpy.fft.fft2 example
ENH: speed-up minimum, maximum and xor for bool dtype
Replaced the operations for the above ufuncs on bools, by simpler
single instructions.

On random inputs `np.minimum` and `np.maximum` run about 25% faster,
and `np.logical_xor` and `np.bitwise_xor` almost 3x faster.
Merge pull request #4740 from jaimefrio/bool-ops

ENH: speed-up minimum, maximum and xor for bool dtype
Merge pull request #4734 from dfreese/feature/nanpercentile

ENH: added functionality nanpercentile to numpy
Merge pull request #4731 from juliantaylor/get-libs-default

BUG: don't set a default for libraries configuration key