gunixconnection: added ngettext to support plural forms
gunixconnection: added ngettext to support plural forms

While those strings ("Expecting 1 control message, got %d" and
"Expecting one fd, but got %d\n") have same singular/plural form
in english, it is not necessarily the case in other languages.

https://bugzilla.gnome.org/show_bug.cgi?id=695233

cention-sany/glib,MathieuDuponchelle/glib,mzabaluev/glib,krichter722/glib,tamaskenez/glib,ieei/glib,lukasz-skalski/glib,cosimoc/glib,krichter722/glib,gale320/glib,mzabaluev/glib,MathieuDuponchelle/glib,Distrotech/glib,johne53/MB3Glib,Distrotech/glib,MathieuDuponchelle/glib,gale320/glib,mzabaluev/glib,gale320/glib,Distrotech/glib,johne53/MB3Glib,cention-sany/glib,tamaskenez/glib,johne53/MB3Glib,MathieuDuponchelle/glib,ieei/glib,lukasz-skalski/glib,endlessm/glib,ieei/glib,cosimoc/glib,cention-sany/glib,tamaskenez/glib,ieei/glib,cosimoc/glib,krichter722/glib,mzabaluev/glib,tchakabam/glib,krichter722/glib,lukasz-skalski/glib,gale320/glib,tchakabam/glib,johne53/MB3Glib,tamaskenez/glib,mzabaluev/glib,lukasz-skalski/glib,lukasz-skalski/glib,johne53/MB3Glib,cosimoc/glib,endlessm/glib,cention-sany/glib,cosimoc/glib,endlessm/glib,Distrotech/glib,Distrotech/glib,johne53/MB3Glib,endlessm/glib,endlessm/glib,tchakabam/glib,tamaskenez/glib,krichter722/glib,tchakabam/glib,cention-sany/glib,ieei/glib,gale320/glib,tchakabam/glib,MathieuDuponchelle/glib