Macro 'testMMMode' checks whether opcode is an MM opcode.

Plus, this commit removes useless 'tm' parameters in 'op_*' macros.

In arithmetic/bitwise operators, the call to metamethods is made
in a separate opcode following the main one. (The main
opcode skips this next one when the operation succeeds.) This
change reduces slightly the size of the binary and the complexity
of the arithmetic/bitwise opcodes. It also simplfies the treatment
of errors and yeld/resume in these operations, as there are much
fewer cases to consider. (Only OP_MMBIN/OP_MMBINI/OP_MMBINK,
instead of all variants of all arithmetic/bitwise operators.)

Several small changes from feedback on 5.4 alhpa rc1 (warnings,
typos in the manual, and the like)

This new field gets the length of 'source' in the same structure.
Unlike the other strings in that structure, 'source' can be
relatively large, and Lua already has its length readily available.

It is an error for a to-be-closed variable to have a non-closable
non-nil value when it is being closed. This situation does not seem to
be useful and often hints to an error. (Particularly in the C API, it is
easy to change a to-be-closed index by mistake.)

Added opcodes for all seven arithmetic operators with K operands
(that is, operands that are numbers in the array of constants of
the function). They cover the cases of constant float operands
(e.g., 'x + .0.0', 'x^0.5') and large integer operands (e.g.,
'x % 10000').

"Better" and similar to error messages for invalid function arguments.
  *old message: 'for' limit must be a number
  *new message: bad 'for' limit (number expected, got table)

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