Use Automake 1.12 for Travis

"make check" doesn't work for Automake 1.11 or earlier.  Let's get a
newer version from a PPA.

.travis.yml

@@ -4,10 +4,13 @@ env:
 before_install:
   # PPA for stable Emacs packages
   - sudo add-apt-repository -y ppa:cassou/emacs
+  # PPA for Automake 1.12
+  - sudo add-apt-repository -y ppa:dns/gnu
   - sudo apt-get update -qq
-  - sudo apt-get install -qq -yy ${EMACS}-nox texinfo
+  - sudo apt-get install -qq -yy ${EMACS}-nox texinfo automake
 script:
   - emacs --version
+  - automake --version
   - autoreconf -i
   - ./configure
   - make all check