Fixes memory alignment problems on Sparc64.

Not quite standard construction, i should add
some autoconf macro.

Not tested yet.

lib/mempool.c

@@ -27,6 +27,7 @@
 struct lp_chunk {
   struct lp_chunk *next;
   unsigned int size;
+  uintptr_t data_align[0];
   byte data[0];
 };
 

lib/resource.c

@@ -250,6 +250,7 @@ resource_init(void)
 struct mblock {
   resource r;
   unsigned size;
+  uintptr_t data_align[0];
   byte data[0];
 };
 

lib/slab.c

@@ -62,6 +62,7 @@ static struct resclass sl_class = {
 
 struct sl_obj {
   node n;
+  uintptr_t data_align[0];
   byte data[0];
 };