replace fabs with something

[trevordblack]

TheNextWeek.html:1588-1595

replace fabs with whatever we typically use locally, ffabs? Make sure correct library is included somewhere

[hollasch]

Interesting. Five occurrences in the books, three in the source.

[hollasch]

Note that fabs and ffabs have different behavior, particularly around NaN.

[hollasch]

Ok, after thinking about this, I believe we should use std::fmin instead of defining our own ffmin, similarly for ffmax, and should continue to use the standard fabs. Doing perf runs shows no significant difference.