Back to how it was, a coroutine does not unwind its stack in case of
errors (and therefore do not close its to-be-closed variables). This
allows the stack to be examined after the error. The program can
use 'coroutine.kill' to close the variables.
The function created by 'coroutine.wrap', however, closes the
coroutine's variables in case of errors, as it is impossible to examine
the stack any way.
New functions to reset/kill a thread/coroutine, mainly (only?) to
close any pending to-be-closed variable. ('lua_resetthread' also
allows a thread to be reused...)
New auxiliary functions/macros 'luaL_argexpected'/'luaL_typeerror'
ease the creation of error messages such as
bad argument #2 to 'setmetatable' (nil or table expected, got boolean)
(The novelty being the "got boolean" part...)
themselves with 'require' (let 'require' do its work); new auxiliary
functions luaL_newlib/luaL_newlibtable/luaL_setfuncs/luaL_requiref.
Old luaL_register will be deprecated.
