docker: Install curl and less in the base test images

Having less available should make debugging in the docker images a bit
more accessible.

Curl is a nice-to-have at the moment, while we also have wget available
from before.

Dockerfile

@@ -3,7 +3,7 @@ FROM ubuntu:18.04
 RUN apt-get update -qq && apt-get install -qqy --no-install-recommends \
     git wget bzip2 file unzip libtool pkg-config cmake build-essential \
     automake yasm gettext autopoint vim python ninja-build subversion \
-    ca-certificates && \
+    ca-certificates curl less && \
     apt-get clean -y && \
     rm -rf /var/lib/apt/lists/*