patch 8.1.1951: mouse double click test is a bit flaky

Problem:    Mouse double click test is a bit flaky.
Solution:   Add to list of flaky tests.  Update a couple of comments.
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 1df7fd9..db6dcd7 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -333,6 +333,7 @@
       \ 'Test_raw_one_time_callback()',
       \ 'Test_reltime()',
       \ 'Test_server_crash()',
+      \ 'Test_term_mouse_double_click_to_create_tab',
       \ 'Test_terminal_ansicolors_default()',
       \ 'Test_terminal_ansicolors_func()',
       \ 'Test_terminal_ansicolors_global()',
diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index a4a7179..1032b45 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -272,7 +272,7 @@
   return cmd
 endfunc
 
-" Get the command to run Vim, with --clean.
+" Get the command to run Vim, with --clean instead of "-u NONE".
 func GetVimCommandClean()
   let cmd = GetVimCommand()
   let cmd = substitute(cmd, '-u NONE', '--clean', '')
diff --git a/src/testdir/test_substitute.vim b/src/testdir/test_substitute.vim
index 344bb68..a263fb6 100644
--- a/src/testdir/test_substitute.vim
+++ b/src/testdir/test_substitute.vim
@@ -504,7 +504,7 @@
   call Run_SubCmd_Tests(tests)
 endfunc
 
-" Test for submatch() on :substitue.
+" Test for submatch() on :substitute.
 func Test_sub_cmd_4()
   set magic&
   set cpo&
diff --git a/src/version.c b/src/version.c
index 156f075..00e82da 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1951,
+/**/
     1950,
 /**/
     1949,