'os.exit' can call lua_close again, separating new finalizers
created after all previous finalizers were already separated.

The flag CIST_FIN does not mark a finalizer, but the function that was
running when the finalizer was called. (So, the function did not call
the finalizer, but it looks that way in the stack.)

As the GC is not reentrant, finalizers should not be able to invoke it.

when building the table 'activelines' for a vararg function, this
first instruction does not make the first line active.

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.

'coroutine.resume' did not increment counter of C calls when
continuing execution after a protected error (that is,
while running 'precover').

Any C function can receive maxinteger as an integer argument, and
therefore cannot increment it without some care (e.g., doing unsigned
arithmetic as the core does).

When calling 'sprintf', not all conversion specifiers accept all
flags; some combinations are undefined behavior.

Added a print with the random seeds used in the tests of 'random'.