Allow user to specify custom token node fields

spec/test_token_user_fields.c

@@ -0,0 +1,30 @@
+#include "testparser.h"
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+int main()
+{
+    char const * input =
+        "# c1\n"
+        "#  c2\n"
+        "\n"
+        "first\n"
+        "\n   \n  \n"
+        "  # s1\n"
+        "   #   s2\n"
+        "second\n";
+    p_context_t * context;
+    context = p_context_new((uint8_t const *)input, strlen(input));
+    assert(p_parse(context) == P_SUCCESS);
+    Start * start = p_result(context);
+
+#ifndef __cplusplus
+    free(context->comments);
+#endif
+    p_context_delete(context);
+    p_tree_delete(start);
+
+    return 0;
+}