Add floor/ceil/round to f64 module #914

Job	Run time
rustfmt	7s
clippy	1m 53s
runefmt	1m 42s
docs	1m 54s
basics	1s
msrv	1m 57s
no_default_features	57s
miri_rune	5m 31s
build_feature (capture-io)	47s
miri_rune_alloc	4m 13s
build_feature (cli,doc)	1m 50s
no_std_minimal	2m 56s
build_feature (cli,fmt)	1m 42s
wasm	1m 9s
build_feature (cli)	1m 41s
build_feature (workspace)	59s
build_feature (languageserver)	1m 49s
build_feature (byte-code)	54s
test	11m 19s
	43m 21s

Provide feedback