This is a conservative change. It does the same thing in weird
cases like the old one. For example, 'sleep abcd' still sleeps
for zero seconds. `sleep 10.a' and `sleep 10.05aa' do the best
and not abort (ie: 10.a == 10 seconds, 10.05a == 10.05 seconds).
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
