BUG: Include sunmath.h in npy_math.h when __SUNPRO_CC defined.

The include is needed for isinf.

Closes #3871.
Merge pull request #3872 from charris/fix-sunpro-issue

BUG: Include sunmath.h in npy_math.h when __SUNPRO_CC defined.
TST: linalg: add more comprehensive test cases for linalg funcs

Also remove TestCase subclassing, so that generator tests work.  Also
fix bugs in the existing generator tests that were not actually run
previously.
BUG: linalg: use correct BLAS incx convention in xCOPY
BUG: linalg: fix eigvalsh return type (always real-valued)
MAINT: linalg: strip out unused gufuncs_linalg code

Some of the functions removed were untested, and apparently did not
function correctly (cholesky_up, inner1d, maybe more).
TST: linalg: add slightly bigger test case + don't catch KeyboardInterrupt
TST: linalg: better rtol choice
Merge pull request #3880 from pv/linalg-stride-fix

Fix bugs in umath_linalg + add more tests + remove unused code
BUG: Disable check for oldstyle classes in python3

Fixes gh-2561
TST: Regression test for gh-2561
DOC: Update 1.8.0 release notes.

Order highlights by significance. This is a subjective judgement.
Mention the linalg enhancements and illustrate with an example.
Update memmap.py

Clarify `memmap` docstring to better reflect the meaning of *offset*.
Merge pull request #3886 from charris/update-1.8.0-notes

DOC: Update 1.8.0 release notes.
Merge pull request #3890 from andreas-h/patch-1

Update memmap.py
TST: Raise AssertionError on failure
Merge pull request #3885 from Nodd/py3_info

BUG: Disable check for oldstyle classes in python3 (np.info)
STY: pepe8 for npyio continued 2 (typo)

fixing one typo in npyio.py
Merge pull request #3829 from jarondl/pep8-npyio

STY: pep8 for npyio
DOC: Notes on backporting.