Added handle_t type to server interface so that we can make handles
pointers later on.
Always use 0 to signal invalid handle in server requests.

diff --git a/scheduler/handle.c b/scheduler/handle.c
index d9a7f8c..0497c64 100644
--- a/scheduler/handle.c
+++ b/scheduler/handle.c
@@ -111,7 +111,7 @@
 HANDLE WINAPI ConvertToGlobalHandle(HANDLE hSrc)
 {
     HANDLE ret = INVALID_HANDLE_VALUE;
-    DuplicateHandle( GetCurrentProcess(), hSrc, (HANDLE)-1, &ret, 0, FALSE,
+    DuplicateHandle( GetCurrentProcess(), hSrc, GetCurrentProcess(), &ret, 0, FALSE,
                      DUP_HANDLE_MAKE_GLOBAL | DUP_HANDLE_SAME_ACCESS | DUP_HANDLE_CLOSE_SOURCE );
     return ret;
 }