Owen Taylor authored Aug 26, 2016 and Christophe Fergeau committed Aug 30, 2016

More recent versions of Xfont have a different API (with namespacing
for libXfont functions.) Check for xfont2.pc and if found, use that, and
use the new API. The rational for preferring libXfont2 is that as a recent
change the xserver module looks for and requires libXfont2, and it's better
not to have both versions of the library in process.