MdePkg/Include: Add support for flexible array members

MdePkg/Include: Add support for flexible array members

Use pragma to disable warning 4200 for all VS* and DDK* tool chains to support
data structure declarations where the last field of the data structure is a
flexible array member.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: lhauch <larry.hauch@intel.com>
Tested-by: Chao Zhang <chao.b.zhang@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17361 6f19259b-4bc3-4df7-8a09-765794883524