For sse2, we don't need to do the fldz/fstp dance when doing a
foreign function call.

A cross-compile is needed!

 * src/bootfiles/20e/boot-2014-04-cross-x86.lisp:
   * Cross-compile script to enable these changes.
 * src/compiler/x86/c-call.lisp:
   * Make the float result tn be xmm registers, not x87 fpu registers.
 * src/compiler/x86/sse2-c-call.lisp:
   * Simplify call-out not to use fldz/fstp except for the minimum
     required for the 32-bit ABI.
 * src/lisp/x86-assem.S
   * Comment out the fstp/fldz insts that aren't needed for SSE2.

entries with just the file path, removing the revision number, date,
author and state.  The actual information is now computed during
compilation and stored in the fasl itself.  (See ticket:48.)

were returned when calling out to a C function returning a float.

float-sse2.lisp:
o Remove the FLOAT-MOVE vop and add a FLOAT-MOVE/SINGLE and
  FLOAT-MOVE/DOUBLE that can handle moving from FR0 or any XMM
  register to any XMM register.
o Update the move vops appropriately.

sse2-c-call.lisp:
o Don't need to move FR0 to XMM0 anymore.  This was one source of the
  problem.  The compiler knows now to ask for a move from FR0 to some
  XMM register.
o Update comments.

vm.lisp:
o Correct printing of XMM registers.  Previously printed them as
  XMM8-15 but should have been XMM0-7.  (Mostly in trace files.)

Carl's suggestion and define new SC numbers for the xmm registers
instead of overloading the x87 fpu registers and the xmm register
SC's.

bootfiles/20a/boot-2010-06-cross-x86.lisp:
o New file needed for cross-compiling this change.

code/x86-vm.lisp:
o Revert previous change.

compiler/x86/sse2-c-call.lisp:
o Use xmm0-tn instead of fr0-tn.  No functional change, but makes the
  code more readable.

compiler/x86/vm.lisp:
o Increase the number of float registers from 8 to 16 (8 more for SSE2
  registers).
o Define new xmm<n> registers
o Update the locations with the new sse2 SC locations for single-reg,
  double-reg, double-double-reg, complex-single-reg,
  complex-double-reg, and complex-double-double-reg storage classes.

lisp/Darwin-os.c:
o Revert previous change.
o Update os_sigcontext_fpu_reg to support the xmm registers.

lisp/Linux-os.c:
o Update os_sigcontext_fpu_reg to support the xmm registers.

boot-2010-02-1 as the bootstrap file.  You should probably also use
the new -P option for build.sh to generate and update the po files
while building.

sse2-packed-2008-11-12).