(find-module-file string) -> pathname or #f
If the given string is a valid path to a file, the pathname for that file will be returned. Otherwise, #f is returned. The directories searched are set via the situation shell script.
Examples:
>> (find-module-file "lib/module.ms") :: "./lib/module.ms" >> (find-module-file "lib/module.mo") :: "./lib/module.mo" >> (find-module-file "bin/glue") :: "./bin/glue" >> (find-module-file "foo/bar") :: #f