This new slider in the White Balance tools allows to alter the computation of
the "auto white balance" by "biasing" it towards warmer or cooler
temperatures. The bias is expressed as a percentage of the computed
temperature, so that the resuling temperature is given by
"computedTemp + computedTemp * bias".
When compiling RT with `-fsanitize=address` it fails early in
`Options::setDefaults()`. To fix it, initialize `baBehav` directly as
permitted with C++11. As a bonus, I converted `addsetids.h` from
defines to an enum.
