Added as incompatibility, in the manual, the extra return of 'io.lines'.

- more consistent nomenclature for error handling
- more precise definition for dead objects
- added algorithm used by 'math.random'
- added luaL_pushfail
- some other minor changes

Corrected several small details: added 'const', adjusts in tabs x
spaces, removed unused #includes and #defines, misspellings, etc.

'simplesect' encloses the introductory text of sections with
subsections, so that each section either is all text or is all
subsections. (This commit also corrects a small brace error in the
manual and extra spaces/tabs in some other files.)

Several small improvements, in particular a new subsection consolidating
all status codes in the API.

Several "metamethods" are not required to be methods (functions),
so it seems clearer not to call them metamethods. The manual now
uses the word 'metavalue' for those values.