Properly use the envp argument in execvPe().
Properly use the envp argument in execvPe().

execvPe() is called by _execvpe(), which we added to implement
posix_spawnp(). We just took execvP() and added the envp argument.
Unfortunately we forgot to change the implementation to use envp over
environ.

This fixes the following piece of code:

| char * const arg[2] = { "env", NULL };
| char * const env[2] = { "FOO=BAR", NULL };
| posix_spawnp(NULL, "/usr/bin/env", NULL, NULL, arg, env);

MFC after:	2 weeks

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase