build: revisit x86_64 build flags yet again

Motivation to add -msse conditionally:

On x86_64, the kernel specifies -mno-sse, with the intention of detecting
accidental use of FP in kernel space.

gcc -m64 -mno-sse rejects the following code, because the ABI places the
return value of double sin(double) in the SSE register %xmm0 (and/or
because the argument :
    extern double sin(double);
    double d;
    void fn() {
        d = sin(d);
    }

rtai for x86_64 is supposed to put -msse in $(rtai-config
--module-cflags), but in rtai-modules-2.6.24-16-rtai 3.6.1-linuxcnc.2
(ubuntu hardy amd64) this is not the case.

Detect this and add -msse by hand if it is not there.  Also, take care
to add it only in kernel space; we're not aware of any reason to have to
add it in userspace.

Motivation to remove -ffast-math, -f[no-]unsafe-math-optimizations:

gcc 4.7.2-5 on debian wheezy miscompiles
    double val;

    void fn(double dot, double radius) {
        val = dot / (radius * radius);
    }
under -Os -ffast-math.  -ffast-math implies -funsafe-math-optimizations,
so specifying it was redundant.  In 2011 I thought I had a report that
-ffast-math -funsafe-math-optimizations was required on one user's amd64
setup, but now that same user reports he has to drop those flags to get
correct behavor, so as far as I know we have no users who need the
-ffast-math flag. (this bug is upstream and fixed:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56125 but the fix looks
unlikely to make it into Debian 7.0's initial release)
Revert "fix building without 5axiskins"

This reverts commit d2bdfa68cfa0206f558db61d9c97f30e9c5483e3.
Revert "Remove bogus sample kins file"

This reverts commit 62d11480ab6091e7d5676884e4d5267218eccf07.
The 5axis sample config uses this!
The tool-length hal pin was vestigial and confusing.
axis: fix state of reload button

this seems to have resulted from a copy-paste error
task: always allow coolant & lube control

Manual control of coolant (both flood and mist) and lube used to be
disabled while Task was in Auto mode and Interp was Running or Waiting.
But it was allowed while Task was in Auto mode and Interp was Idle
or Paused.

This commit enables coolant and lube control in all Interp modes while
Task is in Auto.

I asked if this was change was right and Andy Pugh told me to push it.
axis: always allow coolant and spindle control

Spindle increase/decrease has always been allowed by Task while running
a program, it never made sense for Axis to disallow it.

Coolant (flood & mist, on & off) used to be allowed by Task only in
certain situations (and not while running a gcode program), but that's
no longer the case, so enable Axis control over coolant unconditionally.
Merge remote branch 'origin/v2.5_branch'

Conflicts:
	src/Makefile.modinc.in