R1:769e745a3f27

In charts, make "min" and "max" into pure functions and formally mark pure functions as pure

Summary:
Depends on D20814. Currently, "min()" and "max()" are still "min(f, n)". This is no longer consistent with the construction of functions a function-generators that are composed at top level.

Turn them into "min(n)" and "max(n)" (i.e., not higher-order functions).

Then, mark all the functions which are pure mathematical functions and not higher-order as "pure". These functions have no function parameters…