Update Ubuntu and GCC versions used in Travis build. Now uses GCC 5.4.1. Also, tweaks what builds are run.

.travis.yml

@@ -1,5 +1,5 @@
 sudo: required
-dist: trusty
+dist: xenial
 language: c
 compiler:
   - gcc
@@ -8,15 +8,11 @@ cache:
     - "${HOME}/persist"
 
 before_script:
-# Extra CPython versions
-#  - sudo add-apt-repository -y ppa:fkrull/deadsnakes
-# Extra gcc versions
-#  - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
-  - sudo add-apt-repository -y ppa:terry.guo/gcc-arm-embedded
+  - sudo add-apt-repository -y ppa:team-gcc-arm-embedded/ppa
   - sudo dpkg --add-architecture i386
   - sudo apt-get update -qq || true
   - sudo apt-get install -y python3 gcc-multilib pkg-config libffi-dev libffi-dev:i386 qemu-system gcc-mingw-w64
-  - sudo apt-get install -y --force-yes gcc-arm-none-eabi
+  - sudo apt-get install -y --force-yes gcc-arm-embedded
   # For teensy build
   - sudo apt-get install realpath
   # For coverage testing
@@ -29,8 +25,8 @@ script:
   # Build mpy-cross first because other builds depend on it.
   - make -C mpy-cross
   - make -C atmel-samd BOARD=arduino_zero
-  - make -C atmel-samd BOARD=feather_m0_adalogger
   - make -C atmel-samd BOARD=feather_m0_basic
+  - make -C atmel-samd BOARD=feather_m0_flash
   - make -C atmel-samd BOARD=metro_m0_flash
   - make -C minimal CROSS=1 build/firmware.bin
   - ls -l minimal/build/firmware.bin
@@ -40,16 +36,11 @@ script:
   - 'if [ "$TRAVIS_PULL_REQUEST" = "false" ]; then cp minimal/build/firmware.bin ${HOME}/persist/; fi'
   - make -C unix deplibs
   - make -C unix
-  - make -C unix nanbox
   - make -C bare-arm
   - make -C qemu-arm test
   - make -C stmhal
-  - make -C stmhal -B MICROPY_PY_WIZNET5K=1 MICROPY_PY_CC3K=1
-  - make -C stmhal BOARD=STM32F4DISC
   - make -C teensy
   - make -C cc3200 BTARGET=application BTYPE=release
-  - make -C cc3200 BTARGET=bootloader  BTYPE=release
-  - make -C windows CROSS_COMPILE=i686-w64-mingw32-
 
   # run tests without coverage info
   #- (cd tests && MICROPY_CPYTHON3=python3.4 ./run-tests)