patch 8.0.0508: Coveralls no longer shows per-file coverage

Problem:    Coveralls no longer shows per-file coverage.
Solution:   Add coverage from codecov.io. (Christian Brabandt)
diff --git a/src/version.c b/src/version.c
index 1f82ee1..48f0a4c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    508,
+/**/
     507,
 /**/
     506,