PWR046: Expand to discuss Fortran and add benchmark

[alvrogd]

This PR expands the PWR046 entry to discuss its applicability to Fortran, and adds benchmarks for both C and Fortran. My results:

$ lscpu
  Model name:             13th Gen Intel(R) Core(TM) i7-13700H

$ gcc --version
gcc (Debian 12.2.0-14) 12.2.0

$ gfortran --version
GNU Fortran (Debian 12.2.0-14) 12.2.0

$ ./run-benchmarks.py --check PWR046
------------------------------------------------------------------
Benchmark                        Time             CPU   Iterations
------------------------------------------------------------------
PWR046 C Example              4165 us         4165 us          168
PWR046 C Improved             3035 us         3035 us          232
PWR046 Fortran Example        4154 us         4154 us          167
PWR046 Fortran Improved       3022 us         3022 us          231

[daniel-otero]

Nice!

We need to add a page on the benchmark performance so we don't have to look back on each PR to see a sample.

[alvrogd]

We need to add a page on the benchmark performance so we don't have to look back on each PR to see a sample.

That would be a great idea! I take note of that.