Several details in code (e.g., moving a variable to the most inner
scope that encloses its uses), comments, parameter names, extra tests.

String literal expressions have their own kind VKSTR, instead of the
generic VK. This allows strings to "cross" functions without entering
their constant tables (e.g., if they are used only by some nested
function).

Opcodes OP_NEWTABLE and OP_SETLIST use the same representation to
store the size of the array part of a table. This new representation
can go up to 2^33 (8 + 25 bits).

OP_NEWTABLE is followed by an OP_EXTRAARG, so that it can keep
the exact size of the array part of the table to be created.
(Functions 'luaO_int2fb'/'luaO_fb2int' were removed.)

Local constant variables initialized with compile-time constants
are optimized away from the code.

VLOCAL expressions keep a reference to their corresponding 'Vardesc',
and 'Upvaldesc' (for upvalues) has a field 'ro' (read-only). So, it is
easier to check whether a variable is read-only. The decoupling in
VLOCAL between 'vidx' ('Vardesc' index) and 'sidx' (stack index)
should also help the forthcoming implementation of compile-time
constant propagation.

Added restriction that, when a label is created, there cannot be
another label with the same name visible. That allows backward goto's
to be resolved when they are read. Backward goto's get a close if
they jump out of the scope of some variable; labels get a close only
if previous goto to it jumps out of the scope of some upvalue.

Version numbers and dates (mostly wrong) from RCS keyword strings
removed from all source files; only the file name are kept.