malloc only provides 8byte alignment and is sufficient to load complex
on x86 platforms.
This fixes the f2py alignment failures with complex types on win32 or on
linux32 with -malign-double

Add our python_xerbla to the blasdot sources. That function is
needed for all modules that link to the ATLAS 3.10 libraries, which
in Fedora 21 are located in just two files: libsatlas and libtatlas.

Also make the test for xerbla linkage work better. If xerbla is not
linked the test will be skipped with a message.

SGEMV in Accelerate framework will segfault on MacOS X version 10.9
(aka Mavericks) if arrays are not aligned to 32 byte boundaries
and the CPU supports AVX instructions. This can produce segfaults
in numpy.dot if we use numpy.float32 as dtype. This patch overshadows
the symbols cblas_sgemv, sgemv_ and sgemv exported by Accelerate
to produce the correct behavior. The MacOS X version and CPU specs
are checked on module import. If Mavericks and AVX are detected
the call to SGEMV is emulated with a call to SGEMM if the arrays
are not 32 byte aligned. If the exported symbols cannot be
overshadowed on module import, a fatal error is produced and the
process aborts. All the fixes are in a self-contained C file
and do not alter the _dotblas C code. The patch is not applied
unless NumPy is configured to link with Apple's Accelerate
framework.

BUG: fix crash when sending interrupt signal to fft functions

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.

also rename GCC_ATTRIBUTES to FUNCTION_ATTRIBUTES

the SIGINT handling code must be in the GIL released section so the
longjmp does not skip the retaking.
This implies that the signal handlers must use thread local storage to
avoid a crash when sending interrupt to threaded fft functions.
Distribution of SIGINT to each threads must be handled by the
application as only the master thread receives it
Closes gh-4634

makes attribute checks more sane and allows adding nonnull

Signed-off-by: William Grant <wgrant@ubuntu.com>
Signed-off-by: Michel Normand <normand@linux.vnet.ibm.com>