patch 8.0.1607: --clean loads user settings from .gvimrc

Problem:    --clean loads user settings from .gvimrc.
Solution:   Behave like "-U NONE" was used. (Ken Takata)
diff --git a/runtime/doc/starting.txt b/runtime/doc/starting.txt
index 2358460..9d5e43f 100644
--- a/runtime/doc/starting.txt
+++ b/runtime/doc/starting.txt
@@ -510,11 +510,12 @@
 		{not in Vi}
 
 							*--clean*
---clean		Equal to "-u DEFAULTS -i NONE":
+--clean		Equal to "-u DEFAULTS -U NONE -i NONE":
 		- initializations from files and environment variables is
 		  skipped
 		- the |defaults.vim| script is loaded, which implies
 		  'nocompatible': use Vim defaults
+		- no |gvimrc| script is loaded
 		- no viminfo file is read or written
 		- the home directory is excluded from 'runtimepath'
 							*-x*
diff --git a/src/main.c b/src/main.c
index ff01fd9..61543b1 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1881,6 +1881,9 @@
 		else if (STRNICMP(argv[0] + argv_idx, "clean", 5) == 0)
 		{
 		    parmp->use_vimrc = (char_u *)"DEFAULTS";
+#ifdef FEAT_GUI
+		    use_gvimrc = (char_u *)"NONE";
+#endif
 		    parmp->clean = TRUE;
 		    set_option_value((char_u *)"vif", 0L, (char_u *)"NONE", 0);
 		}
diff --git a/src/version.c b/src/version.c
index 4531c82..e7e3f49 100644
--- a/src/version.c
+++ b/src/version.c
@@ -767,6 +767,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1607,
+/**/
     1606,
 /**/
     1605,