patch 8.1.1506: syntax error in Travis config

Problem:    Syntax error in Travis config.
Solution:   Set AUDIODEV in another section.
diff --git a/src/version.c b/src/version.c
index 13db304..5c12872 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1506,
+/**/
     1505,
 /**/
     1504,