prepare execve args

[sjtobin]

when a new variable is created, we need to update a new char** structure that has the env variables

[crispPacketTriangle]

execve takes char env as a third argument. This is how the environment variables are passed to the executing command. Therefore, when the hashmap is updated with a new variable, it then has to be iterated and a char object created that is substituted for char **env when execve is called (however, the subject doesn't require the possibility of temporary variables)

[sjtobin]

duplicate of #21