Don't redefine existing constants - fix linux build

configure.ac

@@ -1239,7 +1239,7 @@ if test "${SYS}" != "mingw32" -a "${SYS}" != "mingwce"; then
     VLC_ADD_PLUGINS([screensaver motion])
 elif test "${SYS}" != "mingwce"; then
     VLC_ADD_PLUGINS([ntservice access_smb dmo msn])
-    VLC_ADD_LDFLAGS([dmo],[-lole32])
+    VLC_ADD_LDFLAGS([dmo],[-lole32 -luuid])
 else
     VLC_ADD_PLUGINS([win32text])
 fi

modules/codec/dmo/dmo.c

@@ -131,8 +131,6 @@ struct decoder_sys_t
 #endif
 };
 
-const GUID IID_IUnknown = {0x00000000, 0x0000, 0x0000, {0xc0,0x00, 0x00,0x00,0x00,0x00,0x00,0x46}};
-const GUID IID_IClassFactory = {0x00000001, 0x0000, 0x0000, {0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46}};
 const GUID IID_IWMCodecPrivateData = {0x73f0be8e, 0x57f7, 0x4f01, {0xaa, 0x66, 0x9f, 0x57, 0x34, 0xc, 0xfe, 0xe}};
 const GUID IID_IMediaObject = {0xd8ad0f58, 0x5494, 0x4102, {0x97, 0xc5, 0xec, 0x79, 0x8e, 0x59, 0xbc, 0xf4}};
 const GUID IID_IMediaBuffer = {0x59eff8b9, 0x938c, 0x4a26, {0x82, 0xf2, 0x95, 0xcb, 0x84, 0xcd, 0xc8, 0x37}};