CI: compile with libsodium, use distcheck

.travis-libsodium.sh

@@ -0,0 +1,9 @@
+#! /bin/sh
+
+set -e
+
+git clone https://github.com/jedisct1/libsodium.git --branch=stable
+cd libsodium
+./configure --disable-dependency-tracking --enable-minimal --prefix=/usr
+make -j$(nproc) install
+/sbin/ldconfig ||:

.travis.yml

@@ -1,9 +1,14 @@
 language: c
+
 compiler:
  - clang
  - gcc
+
 before_script:
  - sudo apt-get install libldap2-dev libmysqlclient-dev libpq-dev libssl-dev
+ - ./.travis-libsodium.sh
  - ./autogen.sh
  - ./configure --disable-dependency-tracking --with-everything --with-ldap --with-mysql --with-pgsql --with-tls --with-rfc2640
-script: make check
+
+script:
+ - make -j$(nproc) distcheck