* fcntl.cc (fcntl_worker): Remove static storage class.

* flock.cc (flock): Use struct __flock64. Call fcntl_worker.
	Use Cygwin errno functions instead of accessing errno directly.
	* winsup.h: Declare fcntl_worker.

winsup/cygwin/winsup.h

@@ -298,6 +298,8 @@ int symlink_worker (const char *, const char *, bool, bool)
 class path_conv;
 int access_worker (path_conv&, int) __attribute__ ((regparm (2)));
 
+int fcntl_worker (int fd, int cmd, void *arg);
+
 extern "C" int low_priority_sleep (DWORD) __attribute__ ((regparm (1)));
 #define SLEEP_0_STAY_LOW INFINITE