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).

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.

Collisions in short strings occurr just by their existence, when
internalizing them. (Collisions in long strings is caused/controlled
by the program, when adding them as keys to the same table.)

LUA_T* represents only types; tags (types + Variants) are represented
by LUA_V* constants.

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

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

(used only in errors for now)