msacm32: Declare some variables static

[Andrew Talbot]

Changelog:
    msacm32: Declare some variables static.

diff -urN a/dlls/msacm32/internal.c b/dlls/msacm32/internal.c
--- a/dlls/msacm32/internal.c	2006-10-12 21:31:06.000000000 +0100
+++ b/dlls/msacm32/internal.c	2007-01-11 14:16:36.000000000 +0000
@@ -824,8 +824,8 @@
     return MMSYSERR_INVALHANDLE;
 }
 
-PWINE_ACMLOCALDRIVER MSACM_pFirstACMLocalDriver = NULL;
-PWINE_ACMLOCALDRIVER MSACM_pLastACMLocalDriver = NULL;
+static PWINE_ACMLOCALDRIVER MSACM_pFirstACMLocalDriver;
+static PWINE_ACMLOCALDRIVER MSACM_pLastACMLocalDriver;
 
 PWINE_ACMLOCALDRIVER MSACM_RegisterLocalDriver(HMODULE hModule, DRIVERPROC lpDriverProc)
 {