Replace p_context_init() with p_context_new()/p_context_delete()

spec/test_start_rule_tree.c

@@ -6,14 +6,15 @@
 int main()
 {
     char const * input = "hi";
-    p_context_t context;
-    p_context_init(&context, (uint8_t const *)input, strlen(input));
-    assert_eq(P_SUCCESS, p_parse(&context));
-    Top * top = p_result(&context);
+    p_context_t * context;
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert_eq(P_SUCCESS, p_parse(context));
+    Top * top = p_result(context);
     assert(top->pToken != NULL);
     assert_eq(TOKEN_hi, top->pToken->token);
 
     p_free_tree(top);
+    p_context_delete(context);
 
     return 0;
 }