Ruby

Update IO::Buffer#get_value benchmark

• The method was renamed from get to get_value
• Comparing to String#unpack isn't quite equivalent, unpack1 is closer.
• Use frozen_string_literal to avoid allocating a format string every time.
• Use N format which is equivalent to :U32 (uint_32_t big-endian).
• Disable experimental warnings to not mess up the output.