Added global management of user handles in the server.
Very preliminary support for shared window handles.

diff --git a/server/Makefile.in b/server/Makefile.in
index b03708b..1bcfaaa 100644
--- a/server/Makefile.in
+++ b/server/Makefile.in
@@ -36,7 +36,9 @@
 	thread.c \
 	timer.c \
 	trace.c \
-	unicode.c
+	unicode.c \
+	user.c \
+	window.c
 
 PROGRAMS = wineserver