fixed: using size() when serializing strings - this allows to serialize a string which contain a null character

fixed: printing null character in space format: \u0000 (before was \0 which is not correct in json)
fixed: in serialize_string_buffer(const char * input_str, ...) a temporary fixed was used when copying input string
added support for surrogate pairs when reading \uHHHH format
added support to parse \u{H...} format (only if parsing Space format)

tests/main.cpp

@@ -44,9 +44,9 @@
 
 namespace pt
 {
-bool was_error = false;
-int test_counter = 0;
-const char * test_msg = nullptr;
+	bool was_error = false;
+	int test_counter = 0;
+	const char * test_msg = nullptr;
 }