MINOR: ist: Add istend() function to return a pointer to the end of the string

istend() is a shortcut to istptr() + istlen().
diff --git a/include/import/ist.h b/include/import/ist.h
index 4c8979b..1262e8f 100644
--- a/include/import/ist.h
+++ b/include/import/ist.h
@@ -222,6 +222,12 @@
 	return ist.len;
 }
 
+/* returns the pointer to the end the string */
+static inline char *istend(const struct ist ist)
+{
+	return (ist.ptr + ist.len);
+}
+
 /* skips to next character in the string, always stops at the end */
 static inline struct ist istnext(const struct ist ist)
 {