Add a submodule for pi-billion

Instead of having it directly in the repo, which makes it uselessly
heavy.

.gitlab-ci.yml

@@ -9,6 +9,7 @@ stages:
 job test:
   stage: test
   variables:
+    GIT_SUBMODULE_STRATEGY: normal
     SQL_HOST: "localhost"
     SQL_PORT: "3306"
     SQL_DATABASE: "test_$CI_BUILD_REF"

.gitmodules

+[submodule "www/static/pi-billion"]
+	path = www/static/pi-billion
+	url = https://git.laquadrature.net/lqdn-interne/pi-billion.git

app/controller/cron.php

@@ -79,7 +79,7 @@ class Cron extends Controller
                 $template = file_get_contents(dirname(__FILE__)."/../locales/".$pdf['lang']."/LC_MESSAGES/plome.tex");
 
                 // We will open the pi-decimals file
-                $pi = fopen(dirname(__FILE__)."/../static/pi-billion.txt", "rb");
+                $pi = fopen(dirname(__FILE__)."/../static/pi-billion/pi-billion.txt", "rb");
                 if (!$pi) {
                     $logger->write("FATAL: Can't open decimals");
                     exit();

pi-billion @ 46d737de

+Subproject commit 46d737de930450b8703d331f5c122335599d4d39