Throughout, change USE_CYGSERVER to USE_SERVER.

* Makefile.in (LIBSERVER): Define and use.
* configure.in: Set LIBSERVER as appropriate.
* environ.cc: Rename allow_daemon to allow_server.  Only recognize when
USE_SERVER is defined.

winsup/cygwin/shm.cc

@@ -12,7 +12,7 @@ Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
 details. */
 
 #include "winsup.h"
-#ifdef USE_CYGSERVER
+#ifdef USE_SERVER
 #include <sys/types.h>
 
 #include <assert.h>
@@ -690,4 +690,4 @@ client_request_shm::client_request_shm (const key_t key,
 
   msglen (sizeof (_parameters.in));
 }
-#endif /* USE_CYGSERVER */
+#endif /* USE_SERVER */