patch 8.0.0716: not easy to start Vim cleanly

Problem:    Not easy to start Vim cleanly without changing the viminfo file.
            Not possible to know whether the -i command line flag was used.
Solution:   Add the --clean command line argument.  Add the 'viminfofile'
            option.  Add "-u DEFAULTS".
diff --git a/runtime/doc/debug.txt b/runtime/doc/debug.txt
index f539aca..4547eab 100644
--- a/runtime/doc/debug.txt
+++ b/runtime/doc/debug.txt
@@ -1,4 +1,4 @@
-*debug.txt*     For Vim version 8.0.  Last change: 2012 Feb 11
+*debug.txt*     For Vim version 8.0.  Last change: 2017 Jul 15
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -53,7 +53,7 @@
 	valgrind --log-file=valgrind.log --leak-check=full ./vim
 
 Note: Vim will run much slower.  If your .vimrc is big or you have several
-plugins you need to be patient for startup, or run with the "-u NONE"
+plugins you need to be patient for startup, or run with the "--clean"
 argument.
 
 There are often a few leaks from libraries, such as getpwuid() and