Cast void* to char* for pointer arithmetic.

diff --git a/memory/global.c b/memory/global.c
index 17e6b00..0777d99 100644
--- a/memory/global.c
+++ b/memory/global.c
@@ -1621,7 +1621,7 @@
 #endif
     /* FIXME: should do something for other systems */
     GetSystemInfo(&si);
-    lpmem->dwTotalVirtual  = si.lpMaximumApplicationAddress-si.lpMinimumApplicationAddress;
+    lpmem->dwTotalVirtual  = (char*)si.lpMaximumApplicationAddress-(char*)si.lpMinimumApplicationAddress;
     /* FIXME: we should track down all the already allocated VM pages and substract them, for now arbitrarily remove 64KB so that it matches NT */
     lpmem->dwAvailVirtual  = lpmem->dwTotalVirtual-64*1024;
     memcpy(&cached_memstatus,lpmem,sizeof(MEMORYSTATUS));