travis: Add cross-compilation of mingw port

.travis.yml

@@ -7,7 +7,7 @@ before_script:
   - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
   - sudo add-apt-repository -y ppa:terry.guo/gcc-arm-embedded
   - sudo apt-get update -qq
-  - sudo apt-get install -y python3.3 python3 gcc-4.7 gcc-arm-none-eabi qemu-system
+  - sudo apt-get install -y python3.3 python3 gcc-4.7 gcc-arm-none-eabi qemu-system mingw32
 
 script:
   - make -C unix CC=gcc-4.7
@@ -15,6 +15,8 @@ script:
   - make -C bare-arm
   - make -C qemu-arm
   - make -C stmhal
+  - make -C windows CROSS_COMPILE=i586-mingw32msvc-
+
   - (cd tests && MICROPY_CPYTHON3=python3.3 ./run-tests)
 
 after_failure: