Travis: split build using vehicle types

Travis build is timing out because it's taking too much time. Let's
split the build so 1) they can run concurrently and 2) we don't timeout.
We still lose some time due to multiple checkouts, but at least we don't
fail the build due to timeout.

.travis.yml

@@ -17,9 +17,15 @@ notifications:
 
 env:
   global:
-   # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
-   #   via the "travis encrypt" command using the project repo's public key
-   - secure: "FjIwqZQV2FhNPWYITX5LZXTE38yYqBaQdbm3QmbEg/30wnPTm1ZOLIU7o/aSvX615ImR8kHoryvFPDQDWc6wWfqTEs3Ytq2kIvcIJS2Y5l/0PFfpWJoH5gRd6hDThnoi+1oVMLvj1+bhn4yFlCCQ2vT/jxoGfiQqqgvHtv4fLzI="
+    # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
+    #   via the "travis encrypt" command using the project repo's public key
+    - secure: "FjIwqZQV2FhNPWYITX5LZXTE38yYqBaQdbm3QmbEg/30wnPTm1ZOLIU7o/aSvX615ImR8kHoryvFPDQDWc6wWfqTEs3Ytq2kIvcIJS2Y5l/0PFfpWJoH5gRd6hDThnoi+1oVMLvj1+bhn4yFlCCQ2vT/jxoGfiQqqgvHtv4fLzI="
+  matrix:
+    - TRAVIS_BUILD_TYPE=ArduPlane
+    - TRAVIS_BUILD_TYPE=ArduCopter
+    - TRAVIS_BUILD_TYPE=APMrover2
+    - TRAVIS_BUILD_TYPE=AntennaTracker
+    - TRAVIS_BUILD_TYPE=Replay
 
 addons:
   coverity_scan:

Tools/scripts/build_all_travis.sh

@@ -10,6 +10,13 @@ set -x
 
 . ~/.profile
 
+travis_build_type_or_empty() {
+    if [ -z "$TRAVIS_BUILD_TYPE" ] || [ "$TRAVIS_BUILD_TYPE" = "$1" ]; then
+        return 0
+    fi
+    return 1
+}
+
 echo "Testing ArduPlane build"
 pushd ArduPlane
 for b in apm2; do
@@ -20,6 +27,9 @@ done
 popd
 
 for d in ArduCopter APMrover2 ArduPlane AntennaTracker; do
+    if ! travis_build_type_or_empty "$d"; then
+        continue
+    fi
     pushd $d
     make clean
     make navio -j2
@@ -33,9 +43,11 @@ for d in ArduCopter APMrover2 ArduPlane AntennaTracker; do
     popd
 done
 
-pushd Tools/Replay
-make clean
-make linux -j4
-popd
+if travis_build_type_or_empty "Replay"; then
+    pushd Tools/Replay
+    make clean
+    make linux -j4
+    popd
+fi
 
 exit 0