Release v0.3.1

[0.3.1] [Patch] - 2021-12-16

Added

• wrapped macro implementations of all ops:
  • fetch.h wraps fetch_op to define op
  • direct.h wraps an atomic operation to define that same operation
  • cmpxchg.h wraps cmpxchg_weak_explicit to define any other operation

Changed

• renamed types/intptr.h to stdlib/stdint.h
• std implementation now uses wrapped macros instead of defining whole
  functions directly

Fixed

• std implementation now also uses ATOMIC_LLONG_IS_LOCK_FREE in the create
  functions to make sure the corresponding functions are defined
• std implementation no longer assumes sizeof(T) will return a power of 2