functests: Replace execute with either command or feed_command

Hope this will make people using feed_command less likely: this hides bugs.
Already found at least two:

1. msgpackparse() will show internal error: hash_add() in case of duplicate
   keys, though it will still work correctly. Currently silenced.
2. ttimeoutlen was spelled incorrectly, resulting in option not being set when
   expected. Test was still functioning somehow though. Currently fixed.

test/functional/normal/fold_spec.lua

@@ -4,7 +4,7 @@ local clear = helpers.clear
 local insert = helpers.insert
 local feed = helpers.feed
 local expect = helpers.expect
-local execute = helpers.execute
+local feed_command = helpers.feed_command
 local funcs = helpers.funcs
 local foldlevel = funcs.foldlevel
 local foldclosedend = funcs.foldclosedend
@@ -13,7 +13,7 @@ local eq = helpers.eq
 describe('Folds', function()
   local tempfname = 'Xtest-fold.txt'
   clear()
-  before_each(function() execute('enew!') end)
+  before_each(function() feed_command('enew!') end)
   after_each(function() os.remove(tempfname) end)
   it('manual folding adjusts with filter', function()
     insert([[
@@ -37,8 +37,8 @@ describe('Folds', function()
     18
     19
     20]])
-    execute('4,$fold', '%foldopen', '10,$fold', '%foldopen')
-    execute('1,8! cat')
+    feed_command('4,$fold', '%foldopen', '10,$fold', '%foldopen')
+    feed_command('1,8! cat')
     feed('5ggzdzMGdd')
     expect([[
     1
@@ -54,13 +54,13 @@ describe('Folds', function()
   describe('adjusting folds after :move', function()
     local function manually_fold_indent()
       -- setting foldmethod twice is a trick to get vim to set the folds for me
-      execute('set foldmethod=indent', 'set foldmethod=manual')
+      feed_command('set foldmethod=indent', 'set foldmethod=manual')
       -- Ensure that all folds will get closed (makes it easier to test the
       -- length of folds).
-      execute('set foldminlines=0')
+      feed_command('set foldminlines=0')
       -- Start with all folds open (so :move ranges aren't affected by closed
       -- folds).
-      execute('%foldopen!')
+      feed_command('%foldopen!')
     end
 
     local function get_folds()
@@ -75,16 +75,16 @@ describe('Folds', function()
       -- This test is easy because we just need to ensure that the resulting
       -- fold is the same as calculated when creating folds from scratch.
       insert(insert_string)
-      execute(move_command)
+      feed_command(move_command)
       local after_move_folds = get_folds()
       -- Doesn't change anything, but does call foldUpdateAll()
-      execute('set foldminlines=0')
+      feed_command('set foldminlines=0')
       eq(after_move_folds, get_folds())
       -- Set up the buffer with insert_string for the manual fold testing.
-      execute('enew!')
+      feed_command('enew!')
       insert(insert_string)
       manually_fold_indent()
-      execute(move_command)
+      feed_command(move_command)
     end
 
     it('neither closes nor corrupts folds', function()
@@ -246,8 +246,8 @@ a]], '2,3m0')
     	a
     	a
     ]])
-    execute('set foldmethod=indent', '2', '%foldopen')
-    execute('read ' .. tempfname)
+    feed_command('set foldmethod=indent', '2', '%foldopen')
+    feed_command('read ' .. tempfname)
     -- Just to check we have the correct file text.
     expect([[
     	a
@@ -281,7 +281,7 @@ a]], '2,3m0')
     	a
     	a
     ]])
-    execute('set foldmethod=indent', '3,5d')
+    feed_command('set foldmethod=indent', '3,5d')
     eq(5, funcs.foldclosedend(1))
   end)
   it("doesn't combine folds that have a specified end", function()
@@ -295,7 +295,7 @@ a]], '2,3m0')
 
     }}}
     ]])
-    execute('set foldmethod=marker', '3,5d', '%foldclose')
+    feed_command('set foldmethod=marker', '3,5d', '%foldclose')
     eq(2, funcs.foldclosedend(1))
   end)
   it('splits folds according to >N and <N with foldexpr', function()
@@ -331,8 +331,8 @@ a]], '2,3m0')
     a
     a
     ]])
-    execute('set foldmethod=expr', 'set foldexpr=TestFoldExpr(v:lnum)', '2', 'foldopen')
-    execute('read ' .. tempfname, '%foldclose')
+    feed_command('set foldmethod=expr', 'set foldexpr=TestFoldExpr(v:lnum)', '2', 'foldopen')
+    feed_command('read ' .. tempfname, '%foldclose')
     eq(2, funcs.foldclosedend(1))
     eq(0, funcs.foldlevel(3))
     eq(0, funcs.foldlevel(4))