DOC: fixed correlate docstring.

Replaced correlation formula with corrected version that matches the
numpy implementation. Added comment on possible further different
definitions of correlation. Added examples.
Ensure masked arrays are treated correctly for isclose(..,..,equal_nan=True)
DOC: replaced typeset formulas by pure ASCII equivalents.

Replaced typeset formulas by pure ASCII equivalents. Should now be
easier to read in source files.
MAINT: add NPY_CPU_HAVE_UNALIGNED_ACCESS macro

currently only i386 and amd64, must be used carefully as the compiler
may still be allowed to assume alignment and try to vectorize based on
type size alignment.
Merge pull request #3914 from mhvk/numeric/isclose-mask-safe

BUG Masked arrays treated incorrectly in isclose(..,..,equal_nan=True)
BUG: cov/corrcoef complex input and empty arrays

This preserves the complex (and higher precision float or
object) type of the input array, so that the complex
covariance and correlation coefficients can be calculated.

It also fixes the the behaviour of empty arrays. These will
now either result in a 0x0 result, or a NxN result filled
with NaNs.

A warning is now issued when ddof is too large and the factor
set to 0 so that in this case the result is always NaN or
infinity/negative infinity and never a negative number.

Closes gh-597 and gh-2680
Closes gh-3882 (original pull request)
added spaces to literal string concats

literal string concatination without spaces not
allowed in C++11 anymore
BUG: fix declaration-after-statement

closes gh-3930
MAINT: Define NPY_NO_DEPRECATED_API in struct_ufunc_test.c.src

Removes a compile warning and makes the function use proper macro
replacements. Also fix a pointer type mismatch warning.
Merge pull request #3932 from juliantaylor/windows-annoyance

BUG: fix declaration-after-statement
Merge pull request #3929 from chrodan/strc++11

add spaces to literal string concatination for C++11 compatibility
MAINT: silence warning by casting to right type
MAINT: add npy_memchr for memchr like operations

useful for small sizes where the function call is expensive.
Merge pull request #3913 from bspinnler/fix_correlate_docstring

DOC: fixed correlate docstring.
ENH: improve npy_memchr(p, 0) by using __builtin_ctz (tzcnt on x86)

Improves sparse mask performance by about a factor of three, the worst
case of no consecutive mask elements slows down by about 10%-15%.
Merge pull request #3931 from juliantaylor/memchr-move

move memchr like code to a function
Merge pull request #3933 from charris/add-missing-no-deprecated-api

MAINT: Define NPY_NO_DEPRECATED_API in struct_ufunc_test.c.src
BUG: multiarray/mapping -- address for former renaming of array_ass_big_item

Lead to build failures on s390 (32bit user space).
Patch by Charles Harris
Merge pull request #3936 from charris/forward-port-3935

forward-port-3935
BUG: test_fortran_order_buffer fails on big endian architectures.

The numpy unicode string comparison function does not work correctly
for non-native byte orders. That is a problem needing fixing, but
test_fortran_order_buffer is only needed to check that the buffer
works correctly for fortran order buffers, so let the endianess of
test data be the platform default.