Remove references to PCVOID and LPUINT.
Remove types that don't exist on Windows.

diff --git a/include/mmsystem.h b/include/mmsystem.h
index 0388452..874c676 100644
--- a/include/mmsystem.h
+++ b/include/mmsystem.h
@@ -29,6 +29,7 @@
 
 typedef LPSTR		HPSTR;          /* a huge version of LPSTR */
 typedef LPCSTR		HPCSTR;         /* a huge version of LPCSTR */
+typedef UINT*           LPUINT;
 
 DECLARE_HANDLE(HDRVR);
 DECLARE_HANDLE(HWAVE);