declarations for global variables
  for-loop variables are read only
  floats are printed in decimal with enough digits to be read back correctly.
  more levels for constructors
  table.create
  utf8.offset returns also final position of character
  external strings (that use memory not managed by Lua)
  new functions luaL_openselectedlibs and luaL_makeseed
  major collections done incrementally
  more compact arrays (large arrays use about 60% less memory)
  lua.c loads 'readline' dynamically
  static (fixed) binaries (when loading a binary chunk in memory, Lua can reuse its original memory in some of the internal structures)
  dump and undump reuse all strings
  auxiliary buffer reuses buffer when it creates final string