vim-patch:8.2.2060: check for features implemented with "if"

Problem:    Check for features implemented with "if".
Solution:   Use the Check commands. (Ken Takata, closes vim/vim#7383)

aeb313f355

Cherry-pick test_compiler.vim changes from patch 8.1.2373.

src/nvim/testdir/test_autocmd.vim

@@ -1975,9 +1975,7 @@ func Test_change_mark_in_autocmds()
 endfunc
 
 func Test_Filter_noshelltemp()
-  if !executable('cat')
-    return
-  endif
+  CheckExecutable cat
 
   enew!
   call setline(1, ['a', 'b', 'c', 'd'])

src/nvim/testdir/test_compiler.vim

@@ -1,9 +1,11 @@
 " Test the :compiler command
 
+source check.vim
+source shared.vim
+
 func Test_compiler()
-  if !executable('perl')
-    return
-  endif
+  CheckExecutable perl
+  CheckFeature quickfix
 
   " $LANG changes the output of Perl.
   if $LANG != ''

src/nvim/testdir/test_delete.vim

@@ -1,5 +1,7 @@
 " Test for delete().
 
+source check.vim
+
 func Test_file_delete()
   split Xfile
   call setline(1, ['a', 'b'])
@@ -41,9 +43,7 @@ func Test_recursive_delete()
 endfunc
 
 func Test_symlink_delete()
-  if !has('unix')
-    return
-  endif
+  CheckUnix
   split Xfile
   call setline(1, ['a', 'b'])
   wq
@@ -56,9 +56,7 @@ func Test_symlink_delete()
 endfunc
 
 func Test_symlink_dir_delete()
-  if !has('unix')
-    return
-  endif
+  CheckUnix
   call mkdir('Xdir1')
   silent !ln -s Xdir1 Xlink
   call assert_true(isdirectory('Xdir1'))
@@ -70,9 +68,7 @@ func Test_symlink_dir_delete()
 endfunc
 
 func Test_symlink_recursive_delete()
-  if !has('unix')
-    return
-  endif
+  CheckUnix
   call mkdir('Xdir3')
   call mkdir('Xdir3/subdir')
   call mkdir('Xdir4')

src/nvim/testdir/test_diffmode.vim

@@ -621,9 +621,7 @@ func Test_diff_move_to()
 endfunc
 
 func Test_diffexpr()
-  if !executable('diff')
-    return
-  endif
+  CheckExecutable diff
 
   func DiffExpr()
     " Prepend some text to check diff type detection

src/nvim/testdir/test_fold.vim

@@ -95,9 +95,7 @@ func Test_indent_fold2()
 endfunc
 
 func Test_manual_fold_with_filter()
-  if !executable('cat')
-    return
-  endif
+  CheckExecutable cat
   for type in ['manual', 'marker']
     exe 'set foldmethod=' . type
     new