mciwave: Constify a variable

[Andrew Talbot]

Changelog:
    mciwave: Constify a variable.

diff -urN a/dlls/mciwave/mciwave.c b/dlls/mciwave/mciwave.c
--- a/dlls/mciwave/mciwave.c	2007-05-10 17:30:52.000000000 +0100
+++ b/dlls/mciwave/mciwave.c	2007-05-26 17:35:48.000000000 +0100
@@ -241,7 +241,7 @@
 /**************************************************************************
  * 			WAVE_mciReadFmt	                        [internal]
  */
-static	DWORD WAVE_mciReadFmt(WINE_MCIWAVE* wmw, MMCKINFO* pckMainRIFF)
+static	DWORD WAVE_mciReadFmt(WINE_MCIWAVE* wmw, const MMCKINFO* pckMainRIFF)
 {
     MMCKINFO	mmckInfo;
     long	r;