ENH: ma.asarray() and ma.asanyarray() will pass through input of the correct type.

If x is of type MaskedArray for ma.asarray(x) or any subtype of
MaskedArray for ma.asanyarray(x), these functions will simply return x.
This makes them consistent with their numpy counterparts.

Closes gh-4043.
BUG: Fixed mask_rowcols().

Previous implementation relied on ma.asarray() to always create
a new object.

See gh-4043.
ENH: Make output of get_atlas_info conditional on system_info.verbosity
MAINT: Remove doc/numpybook.

Remove doc/numpybook. It has become outdated in parts and its contents
is now part of the official numpy documentation.
DOC: Document removal of doc/numpybook in 1.9.0 release notes.
ENH: add extended axis and keepdims support to median and percentile
MAINT: revert back to separate median implementation

Merging median and percentile make would break astropy and quantities as
we don't call mean anymore. These packages rely on overriding mean to
add their own median behavior.
Need to INCREF dtype again since PyArray_NewFromDescr steals a reference
Merge pull request #3908 from juliantaylor/median-percentile

add extended axis and keepdims support to percentile and median
BUG: Fix commutativity of {dot,multiply,inner}(scalar, matrix_of_objs)

Fixes #2469 and #4482. Relaxes fail condition to allow subtype as documented.
Merge pull request #4488 from charris/remove-numpybook

MAINT: Remove doc/numpybook.
DOC: Change pyrex to Cython in c-info.how-to-extend.rst.
Remove excessive spacing
Merge pull request #4493 from charris/reference-cython-not-pyrex

DOC: Change pyrex to Cython in c-info.how-to-extend.rst.
doc fixes to 'array-protocol type strings'

The item size is not always used (and not always means exact bytes), and
'O' was not in the table.
explain character codes of dtype.kind

"one of 'biufcSUV'" is not very helpful if it stands alone,
also the 'O' typecode was missing.
"(byte-)string" in PyArrayInterface.typekind docs
ENH: release gil for indexing operations

closes gh-4310
ENH: release gil for put and putmask
DOC: specify that 2d array must be non-empty in np.poly error message.

Fixes #2092. Changes message passed to ValueError.