Improves create_native to use std::vector

 * Improves create_native function to use std::vector
instead of char** to build the list of parameters to
execv icecc-create-env script.

Signed-off-by: Ragner Magalhaes <ragner.magalhaes@gmail.com>
Merge pull request #44 from ragner/fix-create_native

Improves create_native to use std::vector