Add log() and other avr-libc math functions to reference and keywords.txt. [imported]

[cmaglie]

This is Issue 264 moved from a Google Code project.
Added by 2010-05-25T20:40:09.000Z by dmel...@gmail.com.
Please review that bug for more context and additional comments, but update this bug.

Original labels: Type-Enhancement, Priority-Medium, Component-Docs, Component-Build

Original description

Since they are available and people want to use them.

[per1234]

Documentation aspect of this issue moved to arduino/reference-en#522