[PATCH] guiddef.h: Remove GUID_NULL declaration.

[Jacek Caban]

It's declared in cguid.h with proper extern "C".

Signed-off-by: Jacek Caban <jacek(a)codeweavers.com>
---

This matches Windows SDK.

  dlls/msxml3/tests/schema.c      | 1 +
  dlls/rpcrt4/ndr_contexthandle.c | 1 +
  dlls/setupapi/devinst.c         | 1 +
  dlls/setupapi/tests/devinst.c   | 1 +
  include/guiddef.h               | 2 --
  5 files changed, 4 insertions(+), 2 deletions(-)