Fix execvp argv[0] convention.
Fix execvp argv[0] convention.

jakubskopal/node-execpe,foysavas/node-kexec,jprichardson/node-kexec,coleww/node-kexec,jprichardson/node-kexec,jakubskopal/node-execpe,coleww/node-kexec,foysavas/node-kexec,coleww/node-kexec,jprichardson/node-kexec,jakubskopal/node-execpe,foysavas/node-kexec