patch 8.0.0419: test for v:progpath fails on MS-Windows

Problem:    Test for v:progpath fails on MS-Windows.
Solution:   Expand to full path.  Also add ".exe" when the path is an absolute
            path.

src/main.c

@@ -3533,27 +3533,26 @@ time_msg(
 set_progpath(char_u *argv0)
 {
     char_u *val = argv0;
-#ifdef WIN32
-    char_u *path = NULL;
-#else
-    char_u buf[MAXPATHL];
-#endif
 
     /* A relative path containing a "/" will become invalid when using ":cd",
      * turn it into a full path.
-     * On MS-Windows "vim.exe" is found in the current directory, thus also do
+     * On MS-Windows "vim" should be expanded to "vim.exe", thus always do
-     * it when there is no path and the file exists. */
+     * this. */
-    if (!mch_isFullName(argv0))
-    {
 # ifdef WIN32
+    char_u *path = NULL;
+
     if (mch_can_exe(argv0, &path, FALSE) && path != NULL)
 	val = path;
 # else
+    char_u buf[MAXPATHL];
+
+    if (!mch_isFullName(argv0))
+    {
 	if (gettail(argv0) != argv0
 			   && vim_FullName(argv0, buf, MAXPATHL, TRUE) != FAIL)
 	    val = buf;
-# endif
     }
+# endif
     set_vim_var_string(VV_PROGPATH, val, -1);
 # ifdef WIN32
     vim_free(path);

src/os_win32.c

@@ -1921,7 +1921,12 @@ executable_exists(char *name, char_u **path, int use_path)
 	if (mch_getperm(name) != -1 && !mch_isdir(name))
 	{
 	    if (path != NULL)
+	    {
+		if (mch_isFullName(name))
 		    *path = vim_strsave((char_u *)name);
+		else
+		    *path = FullName_save((char_u *)name, FALSE);
+	    }
 	    return TRUE;
 	}
 	return FALSE;

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    419,
 /**/
     418,
 /**/