Fixed two warnings when compiling Ruby extension.

- Fixed the format arg passed to printf on if/ruby/hpdf.c:51. The %X format
  specifier expects an int, but the type being passed to it, HPDF_STATUS is
  defined as a long. Prefixed the two 'X's with 'l's to remove compile warn.

- Resolved 2nd compile warning due to if/ruby/hpdf.c:1989. The iterator in
  the for loop was a HPDF_INT, but it was being compared against the
  'num_ptn' element of an HPDF_DashMode, which is defined as an HPDF_UINT.
  I simply made the iterator an HPDF_UINT as well, since it never needed
  to dip into negative territory anyway.