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.
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
ENH: avoid expensive PyArg_ParseTuple in void operations

Replace simple "Oi|O" unpack with faster specialized unpacking

Improves e.g.:

    nrows, ncols = 365, 10000
    items = np.rec.fromarrays(randn(2,265, 10000), names=['widgets','gadgets'])
    row_idx, colidx = randint(0, nrows, ncols), np.arange(ncols)
    %timeit filtered_items = items[row_idx, col_idx]
    In [7]: %timeit filtered_items = items[row_idx, col_idx]
    1000 loops, best of 3: 1.55 ms per loop

to

    In [7]: %timeit filtered_items = items[row_idx, col_idx]
    1000 loops, best of 3: 706 µs per loop
Merge pull request #4731 from juliantaylor/get-libs-default

BUG: don't set a default for libraries configuration key
BLD: add support for OpenRISC architecture.  Closes gh-4743.

Thanks to @manuelafm for the patch.
Merge pull request #4744 from rgommers/openrisc

BLD: add support for OpenRISC architecture.  Closes gh-4743.
Merge pull request #4721 from juliantaylor/void-index

ENH: avoid expensive PyArg_ParseTuple in void operations