Add lambda special form

src/main.c

@@ -16,6 +16,7 @@ int main(int argc, const char **argv) {
     ucl_state_put(state, "let", ucl_special_create(ucl_special_let));
     ucl_state_put(state, "if", ucl_special_create(ucl_special_if));
     ucl_state_put(state, "defun", ucl_special_create(ucl_special_defun));
+    ucl_state_put(state, "lambda", ucl_special_create(ucl_special_lambda));
     ucl_state_put(state, "setq", ucl_special_create(ucl_special_setq));
     ucl_state_put(state, "progn", ucl_special_create(ucl_special_progn));
 
@@ -23,7 +24,6 @@ int main(int argc, const char **argv) {
     //   - progn
     //   - quote
     //   - iteration
-    //   - lambda
 
     ucl_state_put(state, "print", ucl_builtin_create(ucl_builtin_print));
     ucl_state_put(state, "list", ucl_builtin_create(ucl_builtin_list));
@@ -55,6 +55,7 @@ int main(int argc, const char **argv) {
     //   - car
     //   - cdr
     //   - nth
+    //   - booleans (e.g. not)
 
     if (argc < 2) {
         while (1) {