Bug#734675: fftw3: Fix configury for neon support on arm64 (armv8)

[Wookey]

Source: fftw3
Version: 3.3.3-7
Severity: normal
Tags: patch
User: debian-arm at lists.debian.org
Usertag: arm64

In version 3.3.3-6 arm64 was added to the --enable-neon arch list. This
is correct in principle but doesn't work because both the enabling
compiler option and the compiler define have changed between the 32-bit
armv7 (for which this code was written) and armv8 (the 64-bit arch,
called 'arm64' in debian and 'aarch64' by ARM and GNU triplets).

neon is always enabled on armv8/arm64 unless explictly disabled so the
-mfpu=neon option is not understood by the arm64/aarch64 compiler. Also
__ARM_NEON__ is not defined by the compiler. So this needs changes in
configure.ac and simd-neon.h

However, applying this doesn't in fact get a working build as it exposes
a compiler ICE in the gcc4.8 we are currently using in unstable. But
that should get fixed soon.

Note that full support for arm64 will include enabling double-precision,
as that is available in armv8 neon, and writing code to support it.

Also note that armv8 has fused multiply-accumulate by default, which
apparently needs to be recorded for this package. I failed to understand
exactly what was going on with that so have not changed anything in this
patch, not least because doing so prduced another failure to build, as
have_fma and --enable-neon are deemed incompatible.

-- System Information:
Debian Release: 7.3
  APT prefers stable
  APT policy: (990, 'stable')
Architecture: i386 (i686)

Kernel: Linux 3.2.0-kvm-i386-20110111 (SMP w/1 CPU core)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash
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