Fixed warnings about prototype

Author: sergey-dryabzhinsky

src/python-zstd.c

@@ -167,7 +167,7 @@ void init_cContext( int32_t threads, int32_t level)
     ZSTD_CCtx_setParameter(m_cctx, ZSTD_c_nbWorkers, threads);
 }
 
-void free_cContext()
+void free_cContext(void)
 {
     ZSTD_freeCCtx(m_cctx);
 }

src/python-zstd.h

@@ -129,7 +129,7 @@ static PyObject *ZstdError;
 
 static ZSTD_CCtx* m_cctx;
 
-void free_cContext();
+void free_cContext(void);
 void reset_cContext(int32_t threads, int32_t level);
 void init_cContext( int32_t threads, int32_t level);