BoxedMontyForm: additional explanatory comments for modpow (#749) #2003

Job	Run time
minimal-versions	40s
test (i686-unknown-linux-gnu, 1.83.0, sudo apt update && sudo apt install gcc-multilib)	2m 52s
build (1.83.0, thumbv7em-none-eabi)	1m 53s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	2m 40s
build (1.83.0, wasm32-unknown-unknown)	1m 38s
test (x86_64-unknown-linux-gnu, 1.83.0)	2m 3s
build-benchmarks	54s
build (stable, thumbv7em-none-eabi)	1m 52s
test (x86_64-unknown-linux-gnu, stable)	2m 6s
careful	1m 40s
build (stable, wasm32-unknown-unknown)	1m 40s
clippy	19s
doc	31s
cross (aarch64-unknown-linux-gnu, stable)	4m 4s
miri (x86_64-unknown-linux-gnu)	6m 15s
rustfmt	12s
cross (powerpc-unknown-linux-gnu, stable)	5m 41s
miri (s390x-unknown-linux-gnu)	6m 23s
	43m 23s

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