BUILD: fix build on Solaris 11

htonll()/ntohll() already exist on Solaris 11 with a different declaration,
causing a build error as reported by Jonathan Fisher. They used to exist on
OSX with a #define which allowed us to detect them. It was a bad idea to give
these functions a name subject to conflicts like this. Simply rename them
my_htonll()/my_ntohll() to definitely get rid of the conflict.

This patch must be backported to 1.6.
diff --git a/src/sample.c b/src/sample.c
index 4f89bab..9e6baa8 100644
--- a/src/sample.c
+++ b/src/sample.c
@@ -765,7 +765,7 @@
 {
 	struct chunk *chk = get_trash_chunk();
 
-	*(unsigned long long int *)chk->str = htonll(smp->data.u.sint);
+	*(unsigned long long int *)chk->str = my_htonll(smp->data.u.sint);
 	chk->len = 8;
 
 	smp->data.u.str = *chk;