Fix #134: Increase max command length in vclient

[RiRomain]

As reported in issue #134, I was limited by the max length of the command option in vclient, with the current max length being 512, and my command list being 1938 characters long.

This fix #134 by increasing the command max length to 5120, which should be enough to execute all commands at once.

I've tested the fix locally and detected no issue.