Removed LPxxx handle types that don't exist under Windows.

diff --git a/include/mmsystem.h b/include/mmsystem.h
index 874c676..2bae005 100644
--- a/include/mmsystem.h
+++ b/include/mmsystem.h
@@ -43,6 +43,15 @@
 DECLARE_HANDLE(HMIXEROBJ);
 DECLARE_HANDLE(HMMIO);
 
+typedef HMIDI *LPHMIDI;
+typedef HMIDIIN *LPHMIDIIN;
+typedef HMIDIOUT *LPHMIDIOUT;
+typedef HMIDISTRM *LPHMIDISTRM;
+typedef HMIXER *LPHMIXER;
+typedef HMIXEROBJ *LPHMIXEROBJ;
+typedef HWAVEIN *LPHWAVEIN;
+typedef HWAVEOUT *LPHWAVEOUT;
+
 #include "pshpack1.h"
 
 typedef LRESULT (CALLBACK *DRIVERPROC)(DWORD,HDRVR,UINT,LPARAM,LPARAM);