CI: Update Fedora from 25 to 29, and Debian from Stretch to Buster

This gets us new meson for #281,
and also makes it possible to enable -Ddep11=true for Debian as it's no
longer blocked by too old meson in Stretch.

.travis.yml

@@ -6,10 +6,9 @@ services:
   - docker
 
 before_script:
-  - docker build -t appstream-glib-fedora-25 -f contrib/ci/Dockerfile-fedora-25 .
-  - docker build -t appstream-glib-debian-stretch -f contrib/ci/Dockerfile-debian-stretch .
+  - docker build -t appstream-glib-fedora-29 -f contrib/ci/Dockerfile-fedora-29 .
+  - docker build -t appstream-glib-debian-buster -f contrib/ci/Dockerfile-debian-buster .
 
 script:
-  - docker run -t -v `pwd`:/build appstream-glib-fedora-25 ./contrib/ci/build_and_test.sh -Drpm=true -Ddep11=false
-  # ideally Ddep11=true but meson is too old
-  - docker run -t -v `pwd`:/build appstream-glib-debian-stretch ./contrib/ci/build_and_test.sh -Drpm=false -Ddep11=false
+  - docker run -t -v `pwd`:/build appstream-glib-fedora-29 ./contrib/ci/build_and_test.sh -Drpm=true -Ddep11=false
+  - docker run -t -v `pwd`:/build appstream-glib-debian-buster ./contrib/ci/build_and_test.sh -Drpm=false -Ddep11=true

contrib/ci/Dockerfile-debian-stretch → contrib/ci/Dockerfile-debian-buster

@@ -1,6 +1,6 @@
-FROM debian:stretch
+FROM debian:buster
 
-RUN echo "deb-src http://deb.debian.org/debian/ stretch main" >> /etc/apt/sources.list
+RUN echo "deb-src http://deb.debian.org/debian/ buster main" >> /etc/apt/sources.list
 RUN apt-get update -qq
 RUN apt-get install -yq --no-install-recommends meson libstemmer-dev
 RUN apt-get build-dep -yq appstream-glib

contrib/ci/Dockerfile-fedora-25 → contrib/ci/Dockerfile-fedora-29

@@ -1,4 +1,4 @@
-FROM fedora:25
+FROM fedora:29
 
 RUN dnf -y update
 RUN dnf -y install \