After a major bad collection (one that collects too few objects),
next collection will be major again. In that case, avoid switching
back to generational mode (as it will have to switch again to
incremental to do next major collection).
From the point of view of 'git', all names are relative to the root
directory of the project. So, file names in '$Id:' also should be
relative to that directory: the proper name for test file 'all.lua'
is 'testes/all.lua'.
During generational collection, a userdatum must become gray and
go to a gray list after being traversed (like tables), so that
'correctgraylist' can handle it to its next stage.
This commit also added minimum tests for the generational collector,
including one that would detect this bug.
Roberto Ierusalimschy