patch 8.1.0105: all tab stops are the same

Problem:    All tab stops are the same.
Solution:   Add the variable tabstop feature. (Christian Brabandt,
            closes #2711)
diff --git a/src/testdir/gen_opt_test.vim b/src/testdir/gen_opt_test.vim
index 9d12ea0..a742153 100644
--- a/src/testdir/gen_opt_test.vim
+++ b/src/testdir/gen_opt_test.vim
@@ -136,6 +136,8 @@
       \ 'toolbariconsize': [['', 'tiny', 'huge'], ['xxx']],
       \ 'ttymouse': [['', 'xterm'], ['xxx']],
       \ 'ttytype': [[], []],
+      \ 'varsofttabstop': [['8', '4,8,16,32'], ['xxx', '-1', '4,-1,20']],
+      \ 'vartabstop': [['8', '4,8,16,32'], ['xxx', '-1', '4,-1,20']],
       \ 'viewoptions': [['', 'cursor', 'unix,slash'], ['xxx']],
       \ 'viminfo': [['', '''50', '"30'], ['xxx']],
       \ 'virtualedit': [['', 'all', 'all,block'], ['xxx']],