patch 9.0.1372: test for 'toolbariconsize' may fail

Problem:    Test for 'toolbariconsize' may fail.
Solution:   Only test 'toolbariconsize' when it is supported. (James McCoy,
            closes #12095)

src/testdir/test_options.vim

@@ -1642,6 +1642,8 @@ func Test_string_option_revert_on_failure()
   endif
   if exists('+toolbar')
     call add(optlist, ['toolbar', 'text', 'a123'])
+  endif
+  if exists('+toolbariconsize')
     call add(optlist, ['toolbariconsize', 'medium', 'a123'])
   endif
   if exists('+ttymouse') && !has('gui')

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1372,
 /**/
     1371,
 /**/