Module offsets

Offset constants for arrays and vectors:

• Arrays are [ref-count, ...items]
• Vectors are [ref-count, size, capacity, ...items]

Constants

• ARRAY_ITEMS
• ARRAY_META_COUNT
  Number of prefix fields in an array: RC.
• VECTOR_CAPACITY
• VECTOR_ITEMS
• VECTOR_META_COUNT
  Number of prefix fields in a vector: RC, size, capacity.
• VECTOR_SIZE