xalloc: do not implement xfree() function in non-debug mode.

all it does is add another function call in that situation.

src/xalloc.c

@@ -8,7 +8,6 @@
  *   (at your option) any later version.
  */
 
-#include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 #include "util.h"
@@ -84,8 +83,10 @@ void* xmemdup(const void *src, size_t size) {
     return dest;
 }
 
+#ifdef __DEBUG__
 void xfree(void *ptr) {
 
     CHECK_INPUT(ptr, "xfree");
     free(ptr);
 }
+#endif /* __DEBUG__ */

src/xalloc.h

@@ -11,7 +11,7 @@
 #ifndef __XALLOC_H
 #define __XALLOC_H
 
-#include <stddef.h>
+#include <stdlib.h>
 
 void* xmalloc(size_t);
 
@@ -23,6 +23,10 @@ char* xstrdup(const char *);
 
 void* xmemdup(const void *, size_t);
 
+#ifdef __DEBUG__
 void xfree(void *);
+#else
+#define xfree free
+#endif /* __DEBUG__ */
 
 #endif /* __XALLOC_H */