gnu.cfg: Add all bit operation builtins

[aadanen]

I implemented all of the functions described at https://gcc.gnu.org/onlinedocs/gcc/Built-in-Functions.html except for the ones that have a variable return type based on the arguments. This PR should be a superset of the changes proposed in #8721.

I didn't write any tests because I am not sure what the standard practice is. Should I try to have a test for each tag? I have some tests, but I figured I would ask first.

[chrchr-github]

I didn't write any tests because I am not sure what the standard practice is. Should I try to have a test for each tag? I have some tests, but I figured I would ask first.

A few tests would be nice. The configuration looks pretty standard though, so no need to test every function.

[aadanen]

I think CI-unixish failed because it looks like __builtin_stdc_bit_width is only supported starting with gcc 14.1? https://snapshots.sourceware.org/glibc/trunk/latest/manual/html_node/Bit-Manipulation.html

It appears in the gcc changelog starting in 2023, but the machine uses ubuntu 22.04 which came out in 2022, so that older version of GCC throws an error when it tries to verify the syntax of that test.

we could:

1. update the test runner
2. not have a test for __builtin_stdc_bit_width
3. not support __builtin_stdc_bit_width at all

[chrchr-github]

How about
4. check __GNUC__?