[lubuntu] Set proper display DPI with LXDM

[SpaceCat3000]

Problem:
My laptop incorrectly recognises screen DPI (or PPI, whatever).
Fonts look way to small and antialiasing is not applied as intened.

Todo:
Manually set DPI for Xorg (not just font DPI).
My correct value is 118x118 dpi.

Failed methods:
Providing /etc/X11/xorg.conf OR /usr/share/X11/xorg.conf.d/60-monitor.conf files with options like (none helped):

Section "Monitor"
    Identifier "Monitor0"
    DisplaySize 272 204
    Option "DPI" "118 x 118"
EndSection

Editing /etc/X11/xinit/xserverrc to contain line like (strange, but did not help):

exec /usr/bin/X -dpi 118 -nolisten tcp "$@"

The things that worked:
Firstly straightforward method of uncomenting /etc/alternatives/lxdm.conf file to override server args like:

arg=/usr/bin/X -nr vt07 -dpi 118 -nolisten tcp

did not help as well,
but after some debugging the solution was found in putting arg value within double quotes, like follows:

arg="/usr/bin/X -nr vt07 -dpi 118 -nolisten tcp"

Alternative solution (found in Archlinux wiki):
Run command

xrandr --dpi 118

And place this string in appropriate startup script (like /etc/xdg/Lubuntu/autostart for Lubuntu) if You like this solution.