- fix clap test compile and running issue.
- fix unexpected output in console for clap manual.
- remove duplicated program name in clap manual.
- fix there is no default ctor for clap validator.
- fix fatal scoped pointer return in clap parser and resolver.
- add some lost functions for env namespace according to Rust std library. hiwever some functions are not implemented.
- change some function's signatures located in env namespace.
- reduce some useless error kine in env namespace.