patch 8.2.5112: gui test hangs on MS-Windows

Problem:    Gui test hangs on MS-Windows.
Solution:   Use "!start" to start Vim.

Author: brammool

src/testdir/test_gui.vim

@@ -1594,7 +1594,11 @@ func Test_gui_dialog_file()
     confirm qa
   END
   call writefile(lines, 'Xlines')
-  execute '!' .. GetVimCommand() .. ' -g -f --clean --gui-dialog-file Xdialog -S Xlines'
+  let prefix = '!'
+  if has('win32')
+    let prefix = '!start '
+  endif
+  execute prefix .. GetVimCommand() .. ' -g -f --clean --gui-dialog-file Xdialog -S Xlines'
 
   call WaitForAssert({-> assert_true(filereadable('Xdialog'))})
   call assert_match('Question: Save changes to "Xfile"?', readfile('Xdialog')->join('<NL>'))

src/version.c

@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    5112,
 /**/
     5111,
 /**/