ci: install Turkish locale and make locale tests more reliable

.travis.yml

@@ -104,9 +104,11 @@ addons:
       - gcc-5-multilib
       - gcc-multilib
       - gdb
+      - language-pack-tr
       - libc6-dev-i386
       - libtool
       - llvm-3.9-dev
+      - locales
       - pkg-config
       - unzip
       - valgrind

test/functional/normal/lang_spec.lua

@@ -17,13 +17,7 @@ describe('gu and gU', function()
   end)
 
   describe('works in Turkish locale', function()
-    if helpers.pending_win32(pending) then return end
-
     clear()
-    if eval('has("mac")') ~= 0 then
-      pending("not yet on macOS", function() end)
-      return
-    end
 
     local err = exc_exec('lang ctype tr_TR.UTF-8')
     if err ~= 0 then
@@ -47,13 +41,23 @@ describe('gu and gU', function()
 
     it('with casemap=""', function()
       command('set casemap=')
-      -- expect Turkish locale behavior
+      -- expect either Turkish locale behavior or ASCII behavior
+      local iupper = eval("toupper('i')")
+      if iupper == "İ" then
         insert("iI")
         feed("VgU")
         expect("İI")
         feed("Vgu")
         expect("iı")
+      elseif iupper == "I" then
+        insert("iI")
+        feed("VgU")
+        expect("II")
+        feed("Vgu")
+        expect("ii")
+      else
+        error("expected toupper('i') to be either 'I' or 'İ'")
+      end
     end)
-
   end)
 end)