.travis.yml: enable 32-bit builds

As Ubuntu supports running 32-bit executables based on its multiarch
setup, we can enable the tests on 32-bit configurations as well.

Currently, valgrind fails for 32-bit executables on the 64-bit host.
This requires some more investigation.

.travis.yml

@@ -6,18 +6,18 @@ compiler:
 
 env:
   matrix:
-    - CONF=debug
-    - CONF=release
+    - CONF=debug   BITS=64
+    - CONF=release BITS=64
+    - CONF=debug   BITS=32
+    - CONF=release BITS=32
   global:
     - GITHUB_REPO='miloyip/rapidjson'
-    # prepare for 32/64 bit multi-arch support
-    - BITS=64
     - secure: "HrsaCb+N66EG1HR+LWH1u51SjaJyRwJEDzqJGYMB7LJ/bfqb9mWKF1fLvZGk46W5t7TVaXRDD5KHFx9DPWvKn4gRUVkwTHEy262ah5ORh8M6n/6VVVajeV/AYt2C0sswdkDBDO4Xq+xy5gdw3G8s1A4Inbm73pUh+6vx+7ltBbk="
 
 before_install:
   - sudo add-apt-repository -y ppa:codegear/release
   - sudo apt-get update -qq
-  - sudo apt-get install -y premake4 valgrind
+  - sudo apt-get install -qq premake4 valgrind g++-multilib
 
 install: true
 
@@ -29,7 +29,7 @@ script:
   - make -C build/gmake -f example.make config=${CONF}${BITS}
   - pushd bin
   -  ./unittest_${CONF}_x${BITS}_gmake
-  - valgrind --leak-check=full --error-exitcode=1 ./unittest_${CONF}_x${BITS}_gmake
+  - if [ "$BITS" = 64 ]; then valgrind --leak-check=full --error-exitcode=1 ./unittest_${CONF}_x${BITS}_gmake; fi
   - if [ "$CONF" = "release" ]; then ./perftest_${CONF}_x${BITS}_gmake; fi
   - popd
   - ./build/travis-doxygen.sh;