animkeyframe: rename function to f in TRANSFORM macro
animkeyframe: rename function to f in TRANSFORM macro

f() is a very common idiom for "function" in math formulas. This
simplification actually helps the reading.

gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl