Speedup Parser initialization

Extracted from: #512

Use `rb_hash_lookup2` to check for hash key existence instead
of going through `rb_funcall`.

Co-Authored-By: lukeg <luke.gru@gmail.com>

Author: byroot

ext/json/ext/parser/parser.h

@@ -7,7 +7,7 @@
 # define MAYBE_UNUSED(x) x
 #endif
 
-#define option_given_p(opts, key) RTEST(rb_funcall(opts, i_key_p, 1, key))
+#define option_given_p(opts, key) (!RB_UNDEF_P(rb_hash_lookup2(opts, key, Qundef)))
 
 typedef struct JSON_ParserStruct {
     VALUE Vsource;