MFT: GUID_AC3 should be defined in Mingw-w64 4.0
MFT: GUID_AC3 should be defined in Mingw-w64 4.0

Of course, it's technically a GCC bug, because selectany is broken, but
there is no simple fix for that.

(cherry picked from commit 48d665494c2d23e474081a8b222942068b74b9b3)
Signed-off-by: Jean-Baptiste Kempf <7b85a41a628204b76aba4326273a3ccc74bd009a@videolan.org>

jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2