calc 2.16.0.3 release

The following are the changes in this release:

The segmentation fault as reported in issue #174 has been fixed.
When the `powervalue()` function was expanded to (in `value.c`), to
process complex powers, the author forgot that the function `c_power()`
returns NULL when the result is too large to represent in memory.  Now,
when `c_power()` returns NULL within the `powervalue()` function, the
`E_POWER_4` math error ("Too-large value for power") will be raised.
Thanks go to the GitHub user @mengrj for reporting this problem
in issue #174 in a clear and concise way such that we were able
to fix this problem.

Reduced `MAXCMD` (maximum length of command invocation) in `calv.h`
from 16384 to 5120.  On most systems, commands longer than 5.6k would
hit the soft stack size limit and trigger a stack overflow condition
causing calc to crash with a SIGSEGV (segmentation violation).

If you need a super-long calc commands, consider increasing
the `MAXCMD` value in `calc.h`, and increase the stack size
limits for your calc run.  For example under Linux to increase
the maximum stack size to 2^28 bytes:

    prlimit --stack=268435456 calc

or:

    ulimit -s 49152
    calc

Resolved, as much we can, issue #175.

Recommend `-fstack-protector-all` in `Makefile.local` comments.

Fixed signed integer overflow in `c_power()`.

The `c_power(COMPLEX *c1, COMPLEX *c2, NUMBER *epsilon)` function in
`comfunc.c` no longer triggers a signed integer overflow.

Added `qqbitvalue(NUMBER pos)` to `qmarth.c`: like `qbitvalue(long n)`
but with a NUMBER arg, and will return NULL if the shifted bit is too
large to hold in memory.

Added `zzbitvalue(ZVALUE pos, ZVALUE *res)`: similar to the
`zbitvalue(long n, ZVALUE *res)` function but with a `ZVALUE` arg,
and returns a boolean, and does not call math_error().

Added `ZVALUE _baseb_` to hold the `BASEB` as a `ZVALUE`.
Added `MAXDATA_LOG2` to hold the log base 2 value of `MAXDATA`.
Added `MAXLEN_LOG2` to hold the log base 2 value of `MAXLEN`.
Added `HALF_BITS` as an alias for `BASEB`.

Added to `cal/regress.cal`, regression test 9758 to test for
the condition that issue #174 was about.

Improved the Common Address Sanitizer (ASAN) comments in
`Makefile.config` and `Makefile.local`.

Resolved issue #176.