Add a stub implementation of mprapi.dll.
diff --git a/include/Makefile.in b/include/Makefile.in
index 5aa7ef1..0d9f04b 100644
--- a/include/Makefile.in
+++ b/include/Makefile.in
@@ -180,6 +180,7 @@
 	mmddk.h \
 	mmreg.h \
 	mmsystem.h \
+	mprapi.h \
 	msacm.h \
 	msacmdlg.h \
 	msacmdrv.h \