[tz] [PROPOSED] Simplify zdump average-taking

[Paul Eggert]

On 2022-11-30 18:25, Philip Paeps wrote:
> I can't speak for Paul but this specific change looks primarily like a 
> simplification.  The fact that it improves performance is a happy 
> coincidence.

This particular change's main point was to fix the comment, since we are 
moving to C99 or later. The code simplification was a nicety that's 
independent from the C99 change. The delta to the generated instructions 
was more a note to myself than anything important.

I did run the usual regression tests, as I do with all code changes. You 
can run them too, by invoking "make check" or (my favorite on GNU/Linux) 
"make CFLAGS='$(GCC_DEBUG_FLAGS)' check". Of course the tests are not 
exhaustive.

zdump is by far the biggest performance bottleneck in 'make check' so at 
least one user (namely me) would benefit from a faster zdump, not that 
this change affected zdump's performance significantly.