src/journal.c: Tidy up 5.1 compat
src/journal.c: Use lua_newuserdata for allocation instead of calloc so we get automatic cleanup
Squashed 'vendor/compat-5.2/' changes from 0322560..898ede6


git-subtree-dir: vendor/compat-5.2
git-subtree-split: 898ede60ff63ffffb9a2116a151553b2c0f489b0
Merge commit '748d2d4fe3093c821f9c911202b29f5edf071b26'
src/journal.c: Use newly exposed file abilities of compat-5.2