The change to "assignment not used" breaks symmetry with
"used and not set" and removes the reference to the
specific warning mentioned in /sys/doc/comp.ms.
Also, the patch was half-assed as that it left some typos
in like "used an not set", which this change also fixed.
The expression value of the assignment operation was
returned implicitely by relying on regalloc() on the
right hand side "nod" borrowing the register from nn.
But this only works if nn is a register.
In case of 6c, it can also be a ONAME from a .safe
rathole returned by regsalloc().
This change adds explicit gmove() calls to assign the
expression value. Note that gmove() checks if source
and destination are the same register so it wont emit
redundant move operations in the common case.
The same is applied also to OPREINC and OPOSTINC operations.
for gethunk() to work, all allocators have to use it,
including allocations done by libc thru malloc(),
so the fake allocation functions are mandatory for
everyone.
to avoid duplication the code is moved to cc/compat
and prototypes provided in new cc/compat.h header.
implicit casts would cause spurious "result of operation not used"
warnings such as ape's stdio putc() macro.
make (void) casts non-ops when the casted expression has no
side effects. this avoid spurious warning with ape's assert()
macro.
