Rollup merge of #137357 - syvb:sv/log-docs, r=tgross35

Document results of non-positive logarithms

The integer versions of logarithm functions panic on non-positive numbers. The floating point versions have different, undocumented behaviour (-inf on 0, NaN on <0). This PR documents that.

try-job: aarch64-gnu

Author: matthiaskrgr