tools: rename mksrc2

Signed-off-by: Jean Privat <jean@pryen.org>
tools: ngall.sh starts with ../c_src/nitg

Signed-off-by: Jean Privat <jean@pryen.org>
highlight: add `first_line` and `last_line`

Signed-off-by: Jean Privat <jean@pryen.org>
nitlight: add --first-line  --last-line

Signed-off-by: Jean Privat <jean@pryen.org>
tests: update nitlight

Signed-off-by: Jean Privat <jean@pryen.org>