Revert "Experiment: Explicitly write out the computations of precession"

This reverts commit 1babe81f4b721f82663f84fbd5c15703b2ec661d.

The improvement afforded by explicitly writing out the computation,
given the degree of compiler optimizations, is negligible. In my
profiling, it turned out that the commit improved the performance by 8
CPU cycles on average per function call at the expense of
substantially reduced readability! Not worth it.