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

@@ -3533,31 +3533,30 @@ 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
-     * it when there is no path and the file exists. */
+     * On MS-Windows "vim" should be expanded to "vim.exe", thus always do
+     * this. */
+# 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))
     {
-# ifdef WIN32
-	if (mch_can_exe(argv0, &path, FALSE) && path != NULL)
-	    val = path;
-# else
 	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
+# ifdef WIN32
     vim_free(path);
-#endif
+# endif
 }
 
 #endif /* NO_VIM_MAIN */