Assorted spelling fixes.

diff --git a/include/mmsystem.h b/include/mmsystem.h
index ff28041..7b4d562 100644
--- a/include/mmsystem.h
+++ b/include/mmsystem.h
@@ -215,7 +215,7 @@
 
 
 LRESULT WINAPI DefDriverProc(DWORD_PTR,HDRVR,UINT,LPARAM,LPARAM);
-/* this sounds odd, but it's the way it is. OpenDriverA even disapeared
+/* this sounds odd, but it's the way it is. OpenDriverA even disappeared
  * from latest SDK
  */
 HDRVR 	WINAPI OpenDriverA(LPCSTR szDriverName, LPCSTR szSectionName,