Add bohoomil style to fontconfig-infinality

This commit adds a 'bohoomil' USE flag to fontconfig-infinality and
eselect-lcdfilter that together deliver bohoomil's amazing looking
infinality configuration to Gentoo.

To use this style simply add the 'bohoomil' USE flag an re-emerge
fontconfig-infinality and eselect-lcdfilter. You can then use 'eselect
infinality' and 'eselect lcdfilter' to select the new 'bohoomil' style.

To get *exactly* the same rendering as bohoomil's fontconfig-ultimate
set on Arch it's recommended to disable everything other than
52-infinality.conf from 'eselect fontconfig' as well.