Michael Vrable authored Feb 14, 2008 and Carlos Garcia Campos committed Feb 14, 2008

Though they do not represent glyphs, values such as carriage return can be
found in text strings in PDFDocEncoding.  Provide mappings for these bytes
to Unicode.

Additionally, map unknown characters to U+FFFD instead of U+0000, so that
unknown characters do not result in nulls (which can truncate strings
early, particularly if the string is later re-encoded into null-terminated
UTF-8).