See the complaint on #4039. This doesn't fix that particular
issue (it's somewhat unrelated), but does solve around
a file parsing problem reported by @void-in
* Rewrites helpers to just use cmd_exec, since that works in meterpreter and shell.
* Changes _EOF_ to EOF, since that threw a harmless error in shell
commits
* Prefer using Post mixin API instead of rolling-own implementation
* Fixes whitespace
[SeeRM #5940]