migrate language list to po/LINGUAS file

like it's done in all other projects

configure.ac

@@ -243,8 +243,6 @@ AC_SUBST(GETTEXT_PACKAGE)
 AC_DEFINE_UNQUOTED(GETTEXT_PACKAGE, "$GETTEXT_PACKAGE", [Name of the default gettext domain])
 AC_DEFINE_PATH(MATELOCALEDIR, "${datadir}/locale", [locale directory])
 
-ALL_LINGUAS="af am an ar ast az be bg bn br bs ca ca@valencia cmn crh csb cs cy da de el en_AU en_CA en_GB eo es es_CL es_CO es_MX et eu fa fi fr frp fur fy gl he hi hr hu hy id is it ja jv ka kk km kn ko ku ku_IQ ky lb lt lv mk ml mr ms nb ne nl nn oc pa pl pms pt pt_BR ro ru sc si sk sl sq sr sv ta te th tr ug uk ur uz vi zh_CN zh_HK zh_TW"
-
 AM_GLIB_GNU_GETTEXT
 
 ##############################

po/LINGUAS

@@ -0,0 +1,96 @@
+# please keep this list sorted alphabetically
+#
+af
+am
+an
+ar
+ast
+az
+be
+bg
+bn
+br
+bs
+ca
+ca@valencia
+cmn
+crh
+cs
+csb
+cy
+da
+de
+el
+en_AU
+en_CA
+en_GB
+eo
+es
+es_CL
+es_CO
+es_MX
+et
+eu
+fa
+fi
+fr
+frp
+fur
+fy
+gl
+he
+hi
+hr
+hu
+hy
+id
+is
+it
+ja
+jv
+ka
+kk
+km
+kn
+ko
+ku
+ku_IQ
+ky
+lb
+lt
+lv
+mk
+ml
+mr
+ms
+nb
+ne
+nl
+nn
+oc
+pa
+pl
+pms
+pt
+pt_BR
+ro
+ru
+sc
+si
+sk
+sl
+sq
+sr
+sv
+ta
+te
+th
+tr
+ug
+uk
+ur
+uz
+vi
+zh_CN
+zh_HK
+zh_TW