handle the SVf_UTF8 flag correctly on magic strings passed to Imager::IO's write() and raw_write() methods.
This may misbehave in perl 5.6.x since the UTF8 flag may not be visible in the main SV after SvGETMAGIC(). RT# 83438
document that bounding_box() ignores the transformation matrix supplied to tranform() for fonts. RT# 84106