ci: sync CI scripts with NFD

Notable changes include:
  - support WAF_JOBS env var
  - use two parallel build jobs on Travis-CI
  - use "limited builds" for code-coverage and Travis-CI
  - upgrade Travis-CI osx from xcode8.2 to xcode8.3
  - enable ASan on Travis-CI

Change-Id: I4101499ebc590478d67ec8134c0395c4aafb8fb6
diff --git a/.travis.yml b/.travis.yml
index 66e7c5a..560b094 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,9 @@
 sudo: required
 language: generic
+env:
+  global:
+    - JOB_NAME=limited-build
+    - WAF_JOBS=2
 
 matrix:
   include:
@@ -9,6 +13,7 @@
       env:
         - CXX=g++-4.8
         - NODE_LABELS="Linux Ubuntu Ubuntu-14.04"
+        - BUILD_WITH_ASAN=yes
 
     # Linux/clang
     - os: linux
@@ -16,13 +21,15 @@
       env:
         - CXX=clang++
         - NODE_LABELS="Linux Ubuntu Ubuntu-14.04"
+        - BUILD_WITH_ASAN=yes
 
     # macOS/clang
     # https://docs.travis-ci.com/user/osx-ci-environment/#OS-X-Version
     - os: osx
-      osx_image: xcode8.2
+      osx_image: xcode8.3
       env:
         - NODE_LABELS="OSX OSX-10.12"
+        - BUILD_WITH_ASAN=yes
 
 before_script:
   - ${CXX:-c++} --version