tests: Migrate recent patches of legacy eval test.

As the work of this migration did take quite some time, some changes where
made in master after this branch was started.  These are ported to the new
test file.

test/functional/legacy/eval_spec.lua

@@ -1,34 +1,27 @@
 -- Test for various eval features.
--- Note: system clipboard support is not tested. I do not think anybody will
--- thank me for messing with clipboard.
 
 local helpers = require('test.functional.helpers')
 local feed, insert, source = helpers.feed, helpers.insert, helpers.source
 local clear, execute, expect = helpers.clear, helpers.execute, helpers.expect
 local eq, eval, wait, write_file = helpers.eq, helpers.eval, helpers.wait, helpers.write_file
 
+local function has_clipboard()
+  clear()
+  return 1 == eval("has('clipboard')")
+end
+
 describe('eval', function()
   setup(function()
     write_file('test_eval_setup.vim', [[
-      set encoding=latin1
       set noswapfile
       lang C
 
-      fun RegInfo(reg)
+      fun AppendRegContents(reg)
-        return [
+	  call AppendRegParts(a:reg, getregtype(a:reg), getreg(a:reg), string(getreg(a:reg, 0, 1)), getreg(a:reg, 1), string(getreg(a:reg, 1, 1)))
-	  \ a:reg,
-	  \ getregtype(a:reg),
-	  \ getreg(a:reg),
-	  \ string(getreg(a:reg, 0, 1)),
-	  \ getreg(a:reg, 1),
-	  \ string(getreg(a:reg, 1, 1))
-	  \ ]
       endfun
 
-      fun AppendRegContents(reg)
+      fun AppendRegParts(reg, type, cont, strcont, cont1, strcont1)
-      let x = RegInfo(a:reg)
+	  call append('$', printf('%s: type %s; value: %s (%s), expr: %s (%s)', a:reg, a:type, a:cont, a:strcont, a:cont1, a:strcont1))
-	call append('$', printf('%s: type %s; value: %s (%s), expr: %s (%s)',
-	  \ x[0], x[1], x[2], x[3], x[4], x[5]))
       endfun
 
       command -nargs=? AR :call AppendRegContents(<q-args>)
@@ -526,6 +519,42 @@ describe('eval', function()
       =: type v; value: abc/]].."\x00 (['abc/\x00"..[[']), expr: "abc/]]..'\x00'..[[" (['"abc/]]..'\x00'..[["'])]])
   end)
 
+  -- If the clipboard feature is not available the next test will be sciped.
+  if has_clipboard() then
+    it('system clipboard', function()
+      insert([[
+	Some first line (this text was at the top of the old test_eval.in).
+	
+	Note: system clipboard is saved, changed and restored.
+	
+	clipboard contents
+	something else]])
+      execute('so test_eval_setup.vim')
+      -- Save and restore system clipboard.
+      execute("let _clipreg = ['*', getreg('*'), getregtype('*')]")
+      execute('let _clipopt = &cb')
+      execute("let &cb='unnamed'")
+      execute('5y')
+      execute('AR *')
+      execute('tabdo :windo :echo "hi"')
+      execute('6y')
+      execute('AR *')
+      execute('let &cb=_clipopt')
+      execute("call call('setreg', _clipreg)")
+      expect([[
+	Some first line (this text was at the top of the old test_eval.in).
+	
+	Note: system clipboard is saved, changed and restored.
+	
+	clipboard contents
+	something else
+	*: type V; value: clipboard contents]]..'\00'..[[ (['clipboard contents']), expr: clipboard contents]]..'\00'..[[ (['clipboard contents'])
+	*: type V; value: something else]]..'\00'..[[ (['something else']), expr: something else]]..'\00'..[[ (['something else'])]])
+    end)
+  else
+    pending('system clipboard not available', function() end)
+  end
+
   it('errors', function()
     source([[
       fun ErrExe(str)