nitcc: fix Makefile to compile examples

Signed-off-by: Jean Privat <jean@pryen.org>
nitcc: rename t/ to tests/

Signed-off-by: Jean Privat <jean@pryen.org>
nitcc: Makefile gets a `tests` rule

Signed-off-by: Jean Privat <jean@pryen.org>
nitcc: move sources to a src/ subdirectory

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

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

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