Added PCM converter internal driver.
A few driver handling fixes.

diff --git a/dlls/msacm/wineacm.h b/dlls/msacm/wineacm.h
index 4356cc6..3595abf 100644
--- a/dlls/msacm/wineacm.h
+++ b/dlls/msacm/wineacm.h
@@ -285,7 +285,6 @@
 {
     WINE_ACMOBJ		obj;
     HDRVR      		hDrvr;
-    DRIVERPROC		pfnDriverProc;
     PWINE_ACMDRIVER	pNextACMDriver;
 } WINE_ACMDRIVER;
 
@@ -328,6 +327,10 @@
 /* From msacm32.c */
 extern HINSTANCE MSACM_hInstance32;
 
+/* From pcmcnvtr.c */
+LRESULT CALLBACK	PCM_DriverProc(DWORD dwDevID, HDRVR hDriv, UINT wMsg, 
+				       LPARAM dwParam1, LPARAM dwParam2);
+
 /* Dialog box templates */
 #define DLG_ACMFORMATCHOOSE_ID              70
 #define IDD_ACMFORMATCHOOSE_BTN_HELP        9