fix: try different image for compiling Nailgun client

Also mention OCaml code generation in docs

.drone.yml

@@ -30,7 +30,7 @@ steps:
       - mkdir -p lib
       - curl -o lib/sunshine.jar -L 'http://artifacts.metaborg.org/service/local/artifact/maven/redirect?r=snapshots&g=org.metaborg&a=org.metaborg.sunshine2&v=LATEST'
   - name: setup_gen
-    image: maven
+    image: silkeh/clang
     volumes:
       - name: m2
         path: /root/.m2

tests/basic.spt

@@ -59,8 +59,8 @@ For example, this snippet generates the following Python:
 It generates nearly identical code in
 this simple example for Javascript (just with `"Hello, world!"`
 in place of `r'Hello, world!'`), although it generates a different
-preamble defining Stdio for each language. (Currently, Haskell code
-generation is also supported.)
+preamble defining Stdio for each language. (Currently, Haskell and OCaml
+code generation are also supported.)
 
 There's not much to break down in such a tiny program as this, but let's do
 it. The prefix operator `<<<` could be read as "the default stream receives...",