include: Skeleton header for D3DX8.

include/Makefile.in

diff --git a/include/Makefile.in b/include/Makefile.in
index 60b916a..de8b86a 100644
--- a/include/Makefile.in
+++ b/include/Makefile.in
@@ -104,7 +104,9 @@
 	d3drmdef.h \
 	d3dtypes.h \
 	d3dvec.inl \
+	d3dx8.h \
 	d3dx8core.h \
+	d3dx8math.h \
 	dbghelp.h \
 	dbinit.idl \
 	dbprop.idl \