patch 8.0.0319: insert mode completion does not respect 'backspace'

Problem:    Insert mode completion does not respect "start" in 'backspace'.
Solution:   Check whether backspace can go before where insert started.
            (Hirohito Higashi)

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    319,
 /**/
     318,
 /**/