BUILD/MINOR: memprof fix macOs build.

this platform has a similar malloc_usable_size too.

(cherry picked from commit 534197c72196386d9ac58e23cf3eb39be1e936bc)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/include/haproxy/compat.h b/include/haproxy/compat.h
index 0377564..72dc3dc 100644
--- a/include/haproxy/compat.h
+++ b/include/haproxy/compat.h
@@ -277,6 +277,12 @@
 #include <malloc_np.h>
 #endif
 
+/* macOS has a call similar to malloc_usable_size */
+#if defined(USE_MEMORY_PROFILING) && defined(__APPLE__)
+#include <malloc/malloc.h>
+#define malloc_usable_size malloc_size
+#endif
+
 /* Max number of file descriptors we send in one sendmsg(). Linux seems to be
  * able to send 253 fds per sendmsg(), not sure about the other OSes.
  */