patch 8.0.0880: Travis uses an old Ubuntu version

Problem:    Travis uses an old Ubuntu version.
Solution:   Switch from precise to trusty. (Ken Takata, closes #1897)
diff --git a/src/version.c b/src/version.c
index 784f6c1..19e2a0d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    880,
+/**/
     879,
 /**/
     878,