CI: Freeze the version of "catch" used in the CI

.travis.yml

@@ -36,8 +36,9 @@ addons:
 
 install:
     - pip install --user cpp-coveralls; export PATH=$HOME/.local/bin:$PATH
+    # This version of catch is known to work.
     - wget --directory-prefix $PREFIX/include
-              https://raw.github.com/philsquared/Catch/master/single_include/catch.hpp
+              https://raw.github.com/philsquared/Catch/v1.2.1/single_include/catch.hpp
     - wget 'https://01.org/sites/default/files/asio-1.10.6.tar.gz'
     - tar xf asio-1.10.6.tar.gz -C $PREFIX --strip-components=1
 

appveyor.yml

@@ -43,8 +43,9 @@ install:
       wget --no-check-certificate https://01.org/sites/default/files/asio-1.10.6.tar.gz &&
       7z x asio-1.10.6.tar.gz &&
       7z x -i"!asio*/include" asio-1.10.6.tar)
+  # This version of catch is known to work.
   - if not exist catch (
-      wget --no-check-certificate https://raw.github.com/philsquared/Catch/master/single_include/catch.hpp --directory-prefix catch )
+      wget --no-check-certificate https://raw.github.com/philsquared/Catch/v1.2.1/single_include/catch.hpp --directory-prefix catch )
   - set DEBUG_LIBXML2_PATH=%APPVEYOR_BUILD_FOLDER%\libxml2-x86_64-debug
   - set RELEASE_LIBXML2_PATH=%APPVEYOR_BUILD_FOLDER%\libxml2-x86_64