build,travis: enable strerror override option in build

To get consistent output between Linux & OS X.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

.travis.yml

@@ -22,7 +22,7 @@ install:
   - sh autogen.sh
 
 before_script:
-  - ./configure
+  - ./configure --enable-strerror-override
 
 script:
   - make