patch 8.1.1826: tests use hand coded feature and option checks

Problem:    Tests use hand coded feature and option checks.
Solution:   Use the commands from check.vim in more tests.
diff --git a/src/testdir/test_cscope.vim b/src/testdir/test_cscope.vim
index c776be1..9d69da9 100644
--- a/src/testdir/test_cscope.vim
+++ b/src/testdir/test_cscope.vim
@@ -3,10 +3,7 @@
 source check.vim
 CheckFeature cscope
 CheckFeature quickfix
-
-if !executable('cscope')
-  throw 'Skipped: cscope program missing'
-endif
+CheckExecutable cscope
 
 func CscopeSetupOrClean(setup)
     if a:setup