tests: rename engine `nitg` to `nitg-g` ; alias `nitg` to `nitg-s`

Signed-off-by: Jean Privat <jean@pryen.org>
tests: display binary, name and options of current engine

Signed-off-by: Jean Privat <jean@pryen.org>
make: add --private to newmodel documentation

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>
nitg: fixes iterators crashes for test in 62cdb9a9633767baafb04f66fdad79a46d2e9a69

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>
Merge remote-tracking branch 'alexandre/nitdoc'