I have been experimenting with zcompile to speed up loading sourced
library scripts. I found that .zwc files are not used if their timestamp
is identical to that of the source file. This can occur, for example, if
an installer script installs a script file and zcompiles it immediately
after. The granularity of file system timestamps, at least on my system,
is not sufficient to register a difference.

I think it should be a safe enough assumption that they correspond if
the timestamps are identical. The attached patch allows zsh to use .zwc
files if their timestamp is greater than, or identical to the source
file's timestamp.

- M.