Make weak posix_memalign() private to Solaris

OSX has posix_memalign() but no memalign() and no malloc.h
standard include. So until we have a autoconf based build
system, move this weak helper to the private Solaris header.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/helpers.c b/helpers.c
index 098195c..8ac5823 100644
--- a/helpers.c
+++ b/helpers.c
@@ -1,20 +1,11 @@
-#include <malloc.h>
 #include <stdlib.h>
 #include <errno.h>
 #include <sys/socket.h>
+#include <sys/time.h>
 #include <netinet/in.h>
 
 #include "compiler/compiler.h"
 
-int __weak posix_memalign(void **ptr, size_t align, size_t size)
-{
-	*ptr = memalign(align, size);
-	if (*ptr)
-		return 0;
-
-	return ENOMEM;
-}
-
 int __weak posix_fallocate(int fd, off_t offset, off_t len)
 {
 	return 0;