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 #7383)
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index c51f37f..1873a7a 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -1689,9 +1689,7 @@
 endfunc
 
 func Test_Filter_noshelltemp()
-  if !executable('cat')
-    return
-  endif
+  CheckExecutable cat
 
   enew!
   call setline(1, ['a', 'b', 'c', 'd'])
diff --git a/src/testdir/test_compiler.vim b/src/testdir/test_compiler.vim
index ecf8083..06a37c9 100644
--- a/src/testdir/test_compiler.vim
+++ b/src/testdir/test_compiler.vim
@@ -4,9 +4,7 @@
 source shared.vim
 
 func Test_compiler()
-  if !executable('perl')
-    return
-  endif
+  CheckExecutable perl
   CheckFeature quickfix
 
   " $LANG changes the output of Perl.
diff --git a/src/testdir/test_delete.vim b/src/testdir/test_delete.vim
index b23a3bd..6b49f15 100644
--- a/src/testdir/test_delete.vim
+++ b/src/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 @@
 endfunc
 
 func Test_symlink_delete()
-  if !has('unix')
-    return
-  endif
+  CheckUnix
   split Xfile
   call setline(1, ['a', 'b'])
   wq
@@ -56,9 +56,7 @@
 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 @@
 endfunc
 
 func Test_symlink_recursive_delete()
-  if !has('unix')
-    return
-  endif
+  CheckUnix
   call mkdir('Xdir3')
   call mkdir('Xdir3/subdir')
   call mkdir('Xdir4')
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index aba9c9a..2d6228a 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
@@ -621,9 +621,7 @@
 endfunc
 
 func Test_diffexpr()
-  if !executable('diff')
-    return
-  endif
+  CheckExecutable diff
 
   func DiffExpr()
     " Prepent some text to check diff type detection
diff --git a/src/testdir/test_expr.vim b/src/testdir/test_expr.vim
index 754f856..dde6e77 100644
--- a/src/testdir/test_expr.vim
+++ b/src/testdir/test_expr.vim
@@ -543,9 +543,7 @@
 
 " Test for command-line completion of expressions
 func Test_expr_completion()
-  if !has('cmdline_compl')
-    return
-  endif
+  CheckFeature cmdline_compl
   for cmd in [
 	\ 'let a = ',
 	\ 'const a = ',
diff --git a/src/testdir/test_fold.vim b/src/testdir/test_fold.vim
index 1377983..505ad02 100644
--- a/src/testdir/test_fold.vim
+++ b/src/testdir/test_fold.vim
@@ -95,9 +95,7 @@
 endfunc
 
 func Test_manual_fold_with_filter()
-  if !executable('cat')
-    return
-  endif
+  CheckExecutable cat
   for type in ['manual', 'marker']
     exe 'set foldmethod=' . type
     new