The redirection of stderr towards stdout means calls to "which program" always return something even when "program" is not installed. This patch checks for the return value instead before returning the value. See #814.
Having "set editing-mode vi" in ~/.inputrc can output characters that may induce mininet into (wrongly) thinking a process has failed.
- let the user choose where to install (via PREFIX) - added targets install-mnexec/install-manpages