patch 8.1.0135: undo message delays screen update for CTRL-O u

Problem:    Undo message delays screen update for CTRL-O u.
Solution:   Add smsg_attr_keep(). (closes #3125)

src/message.c

@@ -399,6 +399,20 @@ smsg_attr(int attr, char_u *s, ...)
     return msg_attr(IObuff, attr);
 }
 
+    int
+# ifdef __BORLANDC__
+_RTLENTRYF
+# endif
+smsg_attr_keep(int attr, char_u *s, ...)
+{
+    va_list arglist;
+
+    va_start(arglist, s);
+    vim_vsnprintf((char *)IObuff, IOSIZE, (char *)s, arglist);
+    va_end(arglist);
+    return msg_attr_keep(IObuff, attr, TRUE);
+}
+
 #endif
 
 /*

src/proto.h

@@ -115,6 +115,12 @@ _RTLENTRYF
 #  endif
 smsg_attr(int, char_u *, ...);
 
+int
+#  ifdef __BORLANDC__
+_RTLENTRYF
+#  endif
+smsg_attr_keep(int, char_u *, ...);
+
 int
 #  ifdef __BORLANDC__
 _RTLENTRYF

src/undo.c

@@ -2968,7 +2968,7 @@ u_undo_end(
     }
 #endif
 
-    smsg((char_u *)_("%ld %s; %s #%ld  %s"),
+    smsg_attr_keep(0, (char_u *)_("%ld %s; %s #%ld  %s"),
 	    u_oldcount < 0 ? -u_oldcount : u_oldcount,
 	    _(msgstr),
 	    did_undo ? _("before") : _("after"),

src/version.c

@@ -789,6 +789,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    135,
 /**/
     134,
 /**/