Allow attempting to load a module twice.

This is necessary because FreeBSD/ARM and possibly other platforms use
.init_array and not .ctors, so never call the init functions.  As a
result, we will need the compiler to move to putting the load function
in .init_array and may end up with it being called by both variants.

loader.c

@@ -212,6 +212,13 @@ OBJC_PUBLIC void __objc_load(struct objc_init *init)
 		case NewABI:
 			break;
 	}
+
+	// If we've already loaded this module, don't load it again.
+	if (init->version == ULONG_MAX)
+	{
+		return;
+	}
+
 	assert(init->version == 0);
 	assert((((uintptr_t)init->sel_end-(uintptr_t)init->sel_begin) % sizeof(*init->sel_begin)) == 0);
 	assert((((uintptr_t)init->cls_end-(uintptr_t)init->cls_begin) % sizeof(*init->cls_begin)) == 0);
@@ -315,7 +322,7 @@ OBJC_PUBLIC void __objc_load(struct objc_init *init)
 		}
 	}
 #endif
-	init->version = 0xffffffffffffffffULL;
+	init->version = ULONG_MAX;
 }
 
 #ifdef OLDABI_COMPAT