Update travis to test linux 32/64 and osx with a mix of gcc and clang

.travis/install.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+if [[ $TRAVIS_OS_NAME != 'linux' ]]; then
+  brew update
+  # fix an issue with libtool on travis by reinstalling it
+  brew uninstall libtool;
+  brew install libtool dejagnu;
+else
+  sudo apt-get update
+  sudo apt-get install dejagnu texinfo
+  if [ "$HOST" = i386-pc-linux-gnu ] ; then
+      sudo apt-get install gcc-multilib g++-multilib;
+  fi
+fi