canvas.py: add in some minor control on font setting
canvas.py: add in some minor control on font setting

kanarelo/reportlab,Distrotech/reportlab,kanarelo/reportlab,kanarelo/reportlab,kanarelo/reportlab,Distrotech/reportlab,kanarelo/reportlab,Distrotech/reportlab,Distrotech/reportlab,Distrotech/reportlab