lookup AFM font metrics via glyph code instead of name
lookup AFM font metrics via glyph code instead of name

* lookups by glyph code work consistently across all fonts, including
  Symbol and Zapf Dingbats

nifarius/pdf-reader,eitoball/pdf-reader,nmadura/pdf-reader,yob/pdf-reader,tdenovan/pdf-reader,yob/pdf-reader,gordonbisnor/pdf-reader,yob/pdf-reader,boutil/pdf-reader,tardate/pdf-reader