New port: mac68ksf - Macintosh 68k softfloat.

This commit is all the Makefile glue for the new port which is the mac68k
port with MKSOFTFLOAT set to "yes".

As posted here:
https://mail-index.netbsd.org/port-mac68k/2025/10/14/msg001037.html

Add IEEE 754 versions of
fixdfdi.c fixsfdi.c fixunsdfdi.c fixunssfdi.c
floatdidf.c floatdisf.c floatundidf.c floatundisf.c
These don't FP so are well suited to softfloat implementation.

ARM EABI needs left shift logical too.

Adapt to earm hard float by including softfloat-for-gcc.h even if __ARM_EABI__
so we can get the __aeabi aliases.

branches: 1.14.2;
earm* need __lshldi3

branches: 1.13.2;
add support for __floatunsisf().

Update to C89 style.
Fix name of floatundidf (uns -> un).

Assign quad / softfloat specific ${SRCS} to ${SRCS.quad} / ${SRCS.softfloat}
then append them to ${SRCS}. Those will be used to generate quad / softfloat
symbol lists.

Compile ashldi3.S and lshrdi3.S on m68000.

branches: 1.9.12;
use ${ARCHDIR} instead of ${.CURDIR}/arch/${MACHINE_ARCH} where appropriate
libc builds on pmax again

don't include lshrdi3.c in MI sources, since they're already in MD sources

Note functions that probably can be removed

Fix typo in last change

Enable use of assembly language shift routines on the m68k

clean up Ids; no substantive changes.

update for .S and MACHINE_ARCH

make an arch directory in libc, and move all machine dirs into it

branches: 1.1.1;
Torek's quad stuff from 4.4.