Fix parsing of octal encoded characters
Fix parsing of octal encoded characters

When parsing a string, octal encoded characters were always considered as
described by 3 chars. However, the PDF specification says :

  The number ddd may consist of one, two, or three octal digits;
  high-order overflow shall be ignored. Three octal digits shall be
  used, with leading zeros as needed, if the next character of the
  string is also a digit.

readStringFromStream now conforms with the specification.

Patch from Kjo Hansi Glaz <kjo@a4nancy.net.eu.org>

mfenniak/pyPdf