travis: use bash for travis-autogen.sh

Problem was:
./travis-autogen.sh: 6: ./travis-autogen.sh: CFLAGS+= -Wbad-function-cast: not found
./travis-autogen.sh: 8: ./travis-autogen.sh: CFLAGS+= -Wchar-subscripts: not found
[...]

diff --git a/travis-autogen.sh b/travis-autogen.sh
index d83e07d..2079933 100755 (executable)
--- a/travis-autogen.sh
+++ b/travis-autogen.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Warnings enabled
 CFLAGS="-Wall -Wextra"