* Get rid of the RCS Header stuff.  They're meaningless in git.
 * Add public domain comment to some of the files if the only comment
   was the RCS header.

because it makes breakpoints not work for some reason.

working when tracing, for example

(declaim (ftype (function (double-float) double-float) fact))
(defun fact (x)
  (declare (double-float x))
  (if (= x 1)
      1d0
      (* x (fact (1- x)))))


lisp/x86-lispregs.h
o NetBSD has access to the eflags register

lisp/x86-arch.c:
o Add some debugging prints (disabled).
o The stuff near line 262 about pc-9 pointing to the pushf instruction
  should be conditioned on SC_EFLAGS because that's what decides
  whether we insert the pushf instructions for single stepping.

lisp/Config.x86_darwin:
o Add -mmacosx-version-min=10.4 so the C code can run on Tiger.

lisp/Darwin.c:
lisp/x86-lispregs.h:
o The mcontext slot names have a prefix of "__" on 10.5, but have no
  prefix on 10.4.  Add #define's to make the source code work on either.

code.  Rather than introduce a new FreeBSD case to the x86 sigcontext
member accessor routines, collapse all of the system specific routines
down to a common set of routines.

* code/debug-int.lisp - Disable some Darwin-specific code to debug
  NULL mcontext pointers.

* code/float-trap.lisp - Remove ancient FreeBSD-specific code for
  handling floating point signals.

* code/macros.lisp, code/sap.lisp, compiler/saptran.lisp - Include the
  SAP-REF-LONG setter by default on the x86.

* code/x86-vm.lisp - Remove operating system specific sigcontext
  definitions and sigcontext accessors.  Define the alien sigcontext
  as a system area pointer.  Replace the sigcontext accessors with
  foreign function calls that mask the complexity of the underlying
  sigcontext member access.

* compiler/x86/float.lisp - Unconditionally define STORE-LONG-FLOAT.
  This function is used by the %SET-SAP-REF-LONG VOP that underlies
  the SAP-REF-LONG setter.

* compiler/x86/sap.lisp - Unconditionally define %SET-SAP-REF-LONG.
  In the case where there is not a distinct LONG-FLOAT type, admit
  DOUBLE-FLOAT values instead.  The x87 automatically widens values
  pushed onto stack.  This mirrors the behavior of the SAP-REF-LONG
  VOP.

* lisp/Darwin-os.c, lisp/Linux-os.c - Define functions to access
  sigcontext members of interest to Lisp.  Delete the sc_reg function
  and replace its uses with os_sigcontext_reg which is more suitably
  typed.

* lisp/FreeBSD-os.c - Define functions to access sigcontext members of
  interest to Lisp.  We need to be careful about the SSE and non-SSE
  cases for retrieving x87 registers from the saved machine state.
  Define a low-level SIGFPE handler to intercept floating point traps
  and restore the cleared status word bits based on the signal code.
  Get rid of sc_reg for the reasons noted above.

* lisp/Darwin-os.h, lisp/FreeBSD-os.h - Declare the restore_fpu
  function and define a specialized RESTORE_FPU macro.  Remove the
  sc_reg prototype.

* lisp/Linux-os.h - Remove the sc_reg prototype.

* lisp/os.h - Add prototypes for the new os_sigcontext functions.

* lisp/x86-lispregs.h - Redefine SC_REG and SC_PC to expand out to the
  new os_sigcontext functions.  Redfine SC_SP to expand out to SC_REG.
  Eliminate all platform-specific defintions of SC_PC and SC_SP.

x86-lispregs.h:
o Add SC_EFLAGS macro to access the eflags register (currently only
  for linux and darwin).

x86-arch.c:
o Use the SC_EFLAGS macro to enable/disable single-stepping.
o If SC_EFLAGS is not defined, use the single-step helper stuff.

sigset_t is different from the one used in the Linux kernel.  This means
that we cannot make assignments of sigset_t objects without corrupting
memory.  To work around this problem we update uc_sigmask differently
on Linux than on other systems.  Also, remove x87 control word updates
since the x87 is setup correctly inside call_into_lisp.

reg_NARGS macro on these targets and use SC_REG to replace open-coded
assignments to platform specific sigcontext members in interrupt.c and
os-common.c.  This code could be simplified further by merging the x86
and AMD64 cases into the general case.

lisp.c into the correct <foo>-os.h files.

support for glibc2.