Running tests on more specific versions.

Signed-off-by: Yoan Blanc <yoan@dosimple.ch>

.travis.yml

@@ -9,17 +9,17 @@ go:
   - tip
 
 env:
-  - LIBVIPS=7.42
-  - LIBVIPS=8.2
-  - LIBVIPS=8.3
-  - LIBVIPS=8.4
+  - LIBVIPS=7.42.3
+  - LIBVIPS=8.2.3
+  - LIBVIPS=8.3.3
+  - LIBVIPS=8.4.5
   - LIBVIPS=master
 
 matrix:
   allow_failures:
-    - env: LIBVIPS=7.42
-    - env: LIBVIPS=8.2
-    - env: LIBVIPS=8.3
+    - env: LIBVIPS=7.42.3
+    - env: LIBVIPS=8.2.3
+    - env: LIBVIPS=8.3.3
 
 cache: apt
 
@@ -42,9 +42,13 @@ addons:
 
 # VIPS 8.3.3 requires Poppler 0.30 which is not released on Trusty.
 before_install:
-  - wget https://github.com/jcupitt/libvips/archive/$LIBVIPS.zip
-  - unzip $LIBVIPS
-  - cd libvips-$LIBVIPS
+  - >
+    test $LIBVIPS != "master" \
+      && wget http://www.vips.ecs.soton.ac.uk/supported/${LIBVIPS%.*}/vips-${LIBVIPS}.tar.gz -O vips.tgz \
+      || wget https://github.com/jcupitt/libvips/archive/${LIBVIPS}.tar.gz -O vips.tgz
+  - mkdir libvips
+  - tar xf vips.tgz -C libvips --strip-components 1
+  - cd libvips
   - test -f autogen.sh && ./autogen.sh || ./bootstrap.sh
   - >
     CXXFLAGS=-D_GLIBCXX_USE_CXX11_ABI=0