Correctly align program stacks (#1133)

* Properly align program stacks

* Enforce size being a multiple of 8 bytes

* Correct alignment calculation

* Use an ALIGN8 macro in the stack declaration macro

include/z64.h

@@ -49,6 +49,14 @@
 #define Z_PRIORITY_DMAMGR      16
 #define Z_PRIORITY_IRQMGR      17
 
+#define ALIGN8(val) (((val) + 7) & ~7)
+
+#define STACK(stack, size) \
+    u64 stack[ALIGN8(size) / sizeof(u64)]
+
+#define STACK_TOP(stack) \
+    ((u8*)(stack) + sizeof(stack))
+
 // NOTE: Once we start supporting other builds, this can be changed with an ifdef
 #define REGION_NATIVE REGION_EU