patch 8.0.0501: on MS-Windows ":!start" does not work as expected

Problem:    On MS-Windows ":!start" does not work as expected.
Solution:   When creating a process fails try passing the argument to
            ShellExecute().  (Katsuya Hino, closes #1570)

Author: brammool

runtime/doc/os_win32.txt

@@ -212,10 +212,19 @@ A. You can't!  This is a limitation of the NT console.  NT 5.0 is reported to
    be able to set the blink rate for all console windows at the same time.
 
 							*:!start*
-Q. How can I run an external command or program asynchronously?
-A. When using :! to run an external command, you can run it with "start": >
-	:!start winfile.exe<CR>
-<  Using "start" stops Vim switching to another screen, opening a new console,
+Q. How can I asynchronously run an external command or program, or open a
+   document or URL with its default program?
+A. When using :! to run an external command, you can run it with "start". For
+   example, to run notepad: >
+	:!start notepad
+<   To open "image.jpg" with the default image viewer: >
+        :!start image.jpg
+<   To open the folder of the current file in Windows Explorer: >
+        :!start %:h
+<   To open the Vim home page with the default browser: >
+        :!start http://www.vim.org/
+<
+   Using "start" stops Vim switching to another screen, opening a new console,
    or waiting for the program to complete; it indicates that you are running a
    program that does not affect the files you are editing.  Programs begun
    with :!start do not get passed Vim's open file handles, which means they do

src/os_win32.c

@@ -4008,6 +4008,28 @@ vim_create_process(
 }
 
 
+    static HINSTANCE
+vim_shell_execute(
+    char *cmd,
+    INT	 n_show_cmd)
+{
+#ifdef FEAT_MBYTE
+    if (enc_codepage >= 0 && (int)GetACP() != enc_codepage)
+    {
+	WCHAR *wcmd = enc_to_utf16((char_u *)cmd, NULL);
+	if (wcmd != NULL)
+	{
+	    HINSTANCE ret;
+	    ret = ShellExecuteW(NULL, NULL, wcmd, NULL, NULL, n_show_cmd);
+	    vim_free(wcmd);
+	    return ret;
+	}
+    }
+#endif
+    return ShellExecute(NULL, NULL, cmd, NULL, NULL, n_show_cmd);
+}
+
+
 #if defined(FEAT_GUI_W32) || defined(PROTO)
 
 /*
@@ -4711,6 +4733,7 @@ mch_call_shell(
 	    STARTUPINFO		si;
 	    PROCESS_INFORMATION	pi;
 	    DWORD		flags = CREATE_NEW_CONSOLE;
+	    INT			n_show_cmd = SW_SHOWNORMAL;
 	    char_u		*p;
 
 	    ZeroMemory(&si, sizeof(si));
@@ -4729,6 +4752,7 @@ mch_call_shell(
 		cmdbase = skipwhite(cmdbase + 4);
 		si.dwFlags = STARTF_USESHOWWINDOW;
 		si.wShowWindow = SW_SHOWMINNOACTIVE;
+		n_show_cmd = SW_SHOWMINNOACTIVE;
 	    }
 	    else if ((STRNICMP(cmdbase, "/b", 2) == 0)
 		    && VIM_ISWHITE(cmdbase[2]))
@@ -4800,6 +4824,9 @@ mch_call_shell(
 	     */
 	    if (vim_create_process((char *)newcmd, FALSE, flags, &si, &pi))
 		x = 0;
+	    else if (vim_shell_execute((char *)newcmd, n_show_cmd)
+							       > (HINSTANCE)32)
+		x = 0;
 	    else
 	    {
 		x = -1;

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    501,
 /**/
     500,
 /**/