resolve "function declaration isn't a prototype"

change two declarations in headers to form f(void); instead of f();
which eliminates the warnings when compiling against zeromq
Signed-off-by: MinRK <benjaminrk@gmail.com>

AUTHORS

@@ -38,6 +38,7 @@ Max Wolf <YIDIEPXGXGPN@spammotel.com>
 McClain Looney <m@loonsoft.com>
 Mikael Helbo Kjaer <mhk@designtech.dk>
 Mikko Koppanen <mkoppanen@php.net>
+Min Ragan-Kelley <benjaminrk@gmail.com>
 Nir Soffer <nirsof@gmail.com>
 Pavel Gushcha <pavimus@gmail.com>
 Pavol Malosek <malosek@fastmq.com>

include/zmq.h

@@ -108,7 +108,7 @@ ZMQ_EXPORT void zmq_version (int *major, int *minor, int *patch);
 /*  of this function is to make the code 100% portable, including where 0MQ   */
 /*  compiled with certain CRT library (on Windows) is linked to an            */
 /*  application that uses different CRT library.                              */
-ZMQ_EXPORT int zmq_errno ();
+ZMQ_EXPORT int zmq_errno (void);
 
 /*  Resolves system errors and 0MQ errors to human-readable string.           */
 ZMQ_EXPORT const char *zmq_strerror (int errnum);

include/zmq_utils.h

@@ -45,7 +45,7 @@ extern "C" {
 /*  about minutiae of time-related functions on different OS platforms.       */
 
 /*  Starts the stopwatch. Returns the handle to the watch.                    */
-ZMQ_EXPORT void *zmq_stopwatch_start ();
+ZMQ_EXPORT void *zmq_stopwatch_start (void);
 
 /*  Stops the stopwatch. Returns the number of microseconds elapsed since     */
 /*  the stopwatch was started.                                                */