Xdefaults, xinitrc: dynamically calculate font size

Recent changes in OpenBSD made my laptops share different (althought
correctly calculated) DPIs. Add an script and rework X resources loading
so:

 1. load ~/.Xdefaults into xrdb for baseline
 2. run the script to compute a DPI and xterm's faceSize so it respects
    some values previously defined in this repo

As an upside, now XTerm.VT100.faceSize can be queried, so use that in
hlwm theme.

dotfiles/xinitrc

@@ -1,6 +1,6 @@
 #!/bin/sh
 # env
-# Written in 2019,2021 by Lucas
+# Written in 2019,2021-2022 by Lucas
 # CC0 1.0 Universal/Public domain - No rights reserved
 #
 # To the extent possible under law, the author(s) have dedicated all
@@ -21,9 +21,13 @@ xset r rate 300 75
 
 xset b off
 
+xrdb -load ~/.Xdefaults
 if [ -r ~/.Xresources ]; then
 	xrdb -merge ~/.Xresources
 fi
+if [ -r ~/code/lucas/env/utils/scripts/x-dpi-facesizes.sh ]; then
+	sh ~/code/lucas/env/utils/scripts/x-dpi-facesizes.sh
+fi
 
 : ${logdir:=~/local/var/log}
 exec herbstluftwm -l >"$logdir/hlwm.out" 2>"$logdir/hlwm.err"