configure: Add compiler warning -Wunused-but-set-parameter.
diff --git a/configure.ac b/configure.ac
index 51d0533..82b1783 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1707,6 +1707,7 @@
   WINE_TRY_CFLAGS([-Wdeclaration-after-statement])
   WINE_TRY_CFLAGS([-Wstrict-prototypes])
   WINE_TRY_CFLAGS([-Wtype-limits])
+  WINE_TRY_CFLAGS([-Wunused-but-set-parameter])
   WINE_TRY_CFLAGS([-Wwrite-strings])
 
   dnl Check for noisy string.h