Compile fix for multi-threaded perl.

diff --git a/programs/winetest/winetest.c b/programs/winetest/winetest.c
index 04074e0..3e9e673 100644
--- a/programs/winetest/winetest.c
+++ b/programs/winetest/winetest.c
@@ -152,7 +152,7 @@
 
 
 /* perl extension initialisation */
-static void xs_init(void)
+static void xs_init(pTHX)
 {
     extern void boot_wine(CV *cv);
     newXS("wine::bootstrap", boot_wine,__FILE__);