better optimization options

last changes by lhf.

wrong assert

entry for new version (4.0a)

new format for numbers in precompiled code (as strings)

new version is beta.

"exp" changed to "exp0" to avoid problems with math.h.

module to load bytecodes from files.

for security reasons, one cannot change the tag of a udata

from Lua.

mem.h is now luamem.h

removed warn
added support for new opcodes (VARARGS, STOREMAP)
better error messages with luaL_verror