Turns out it was only used once in the whole tree.

malloc(0) can legally be NULL (or not unique).

I don't have the courage to replace all the occurences in the code.

Also sizeof(byte_t)^Wsizeof(uint8_t) can only ever be 1, if it is
defined. It's not defined, if char is more than 8 bits, and uint8_t is
not provided, but then VLC will not compile in the first place.

by using VLC_ADD_PLUGIN instead of VLC_ADD_BUILTINS.

Please check for potential regressions.

In the function ExecuteCommand, p_message is given in argument to ExecuteHelp
and is then modified locally in ExecuteHelp:
  p_message = vlm_MessageNew( "help", vlm_NULL );
whereas it is used further in function ExecuteCommand.
This patch fixes this problem by passing the pointer address in argument to
ExecuteHelp instead of the pointer itself.
Signed-off-by: Pierre d'Herbemont <pdherbemont@videolan.org>

This closes #1565