tests: update testing of nitc.nit

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

squash-test-rename
man: rename nitg to nitc

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

Signed-off-by: Jean Privat <jean@pryen.org>
bin: add compatibility shell script for nitg

Signed-off-by: Jean Privat <jean@pryen.org>
contrib&examples: Makefiles use nitc instead of nitg

Signed-off-by: Jean Privat <jean@pryen.org>
benchmarks: use nitc instead of nitg

Signed-off-by: Jean Privat <jean@pryen.org>
bash_completion: switch nitg and nitc

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