.travis.yml: update to xenial; add jobs for ubsan and asan (#1745)

As tested by @matthiaskrgr in the branch
https://github.com/matthiaskrgr/cppcheck/commits/travis_xenial
Add job to build Cppcheck on Ubuntu 14.04 trusty (same as for precise).

.travis.yml

@@ -1,5 +1,5 @@
 language: cpp
-dist: trusty
+dist: xenial
 
 compiler:
   - gcc
@@ -28,6 +28,16 @@ matrix:
       compiler: clang
 # defined extra jobs that run besides what is configured in the build matrix
   include:
+# -fsanitize=undefined
+    - name: "undefined behaviour sanitizers"
+      compiler: gcc
+      script:
+        - CXXFLAGS="-fsanitize=undefined -fno-sanitize-recover=all -Og -g3" make cppcheck test checkcfg -j 2
+# -fsanitize=address
+    - name: "address sanitizers"
+      compiler: gcc
+      script:
+         - CXXFLAGS="-fsanitize=address -Og -g3" make cppcheck test checkcfg -j 2
 # check a lot of stuff that only needs to be checked in a single configuration
     - name: "misc"
       compiler: clang
@@ -162,6 +172,17 @@ matrix:
         - CXX=g++ CXXFLAGS="${ORIGINAL_CXXFLAGS}" make cppcheck testrunner -j 2
         - make clean
         - CXX=clang++ CXXFLAGS="${ORIGINAL_CXXFLAGS}" make cppcheck testrunner -j 2
+# check if cppcheck builds on trusty
+    - name: "make ubuntu 14.04 trusty"
+      compiler: gcc
+      dist: trusty
+      before_install:
+        - sudo apt-get update -qq
+        - sudo apt-get install libxml2-utils libpcre3
+      script:
+        - CXX=g++ CXXFLAGS="${ORIGINAL_CXXFLAGS}" make cppcheck testrunner -j 2
+        - make clean
+        - CXX=clang++ CXXFLAGS="${ORIGINAL_CXXFLAGS}" make cppcheck testrunner -j 2
 # check if cppcheck builds on osx
     - name: "make osx"
       os: osx