~/.Xresources: Enable autohinting for urxvt.

I don't know why, actually...

.Xresources

URxvt*font:                 xft:Monaco for Powerline:regular:size=11
URxvt*imFont:               xft:Monaco for Powerline:regular:size=11
URxvt*boldFont:             xft:Monaco for Powerline:bold:size=11
URxvt*italicFont:           xft:Monaco for Powerline:italic:size=11
URxvt*italicFont:           xft:Monaco for Powerline:italic:size=11:autohint=true
URxvt*boldItalicFont:       xft:Monaco for Powerline:bold:italic:size=11
URxvt.perl-ext-common:      default,url-select