Several definitions that don't need to be "global" (that is, that
concerns only specific parts of the code) moved out of llimits.h,
to more appropriate places.
The generational mode also uses the parameters for the incremental
mode in its major collections, so it should be easy to change those
parameters without having to change the GC mode.
'lua_resetthread' is back to its original signature, to avoid
incompatibilities in the ABI between releases of the same version.
New function 'lua_closethread' added with the "correct" signature.
When closing variables during 'coroutine.close' or 'lua_resetthread',
the status of a coroutine must be set to LUA_OK; a coroutine should
not run with any other status. (See assertion in 'lua_callk'.)
After the reset, the status should be kept as normal, as any error
was already reported.
Instead of assuming that shrinking a block may be an emergency
collection, use an explicit field ('gcstopem') to stop emergency
collections while GC is working.
More uses of macros 'likely'/'unlikely' (renamed to
'l_likely'/'l_unlikely'), both in range (extended to the
libraries) and in scope (extended to hooks, stack growth).
To-be-closed variables are linked in their own list, embedded into the
stack elements. (Due to alignment, this information does not change
the size of the stack elements in most architectures.) This new list
does not produce garbage and avoids memory errors when creating tbc
variables.
Initial implementation to allow yields inside '__close' metamethods.
This current version still does not allow a '__close' metamethod
to yield when called due to an error. '__close' metamethods from
C functions also are not allowed to yield.
When a stack grows, its extra area can be in use, and it becomes part
of the common area. So, the extra area must be kept correct all the
times. (Bug introduced by commit 5aa36e894f5.)
Hashes for long strings are computed only when they are used as keys
in a table, not a too common case. And, in that case, it is to easy to
force collisions changing only the characters which are not part of the
hash.
The stack size is derived from 'stack_last', when needed. Moreover,
the handling of stack sizes is more consistent, always excluding the
extra space except when allocating/deallocating the array.
The previous stackless implementations marked all 'luaV_execute'
invocations as fresh. However, re-entering 'luaV_execute' when
resuming a coroutine should not be a fresh invocation. (It works
because 'unroll' called 'luaV_execute' for each call entry, but
it was slower than letting 'luaV_execute' finish all non-fresh
invocations.)
