Travis CI: add clang and osx

Extend builds to clang and osx platforms.

And check bench numbers.

No functional change.

.travis.yml

@@ -1,14 +1,32 @@
 language: cpp
-compiler: g++
-sudo: required
 
-before_install:
-  - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
-  - sudo apt-get update -qq
+matrix:
+  include:
+    - os: linux
+      compiler: gcc
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test']
+          packages: ['g++-4.8']
+      env:
+        - COMPILER=g++-4.8
+        - COMP=gcc
 
-install:
-  - sudo apt-get install -qq g++-4.8
-  - sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.8 90
+    - os: linux
+      compiler: clang
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.7']
+          packages: ['clang-3.7']
+      env:
+        - COMPILER=clang++-3.7
+        - COMP=clang
+
+    - os: osx
+      compiler: clang
+      env:
+        - COMPILER=clang++ V='Apple LLVM 6.0' # Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn)
+        - COMP=clang
 
 branches:
   only:
@@ -18,5 +36,8 @@ before_script:
   - cd src
 
 script:
-  - make clean && make build ARCH=x86-64 COMP=gcc && ./stockfish bench 2>&1 >/dev/null | grep 'Nodes searched'
-  - make clean && make build ARCH=x86-32 COMP=gcc && ./stockfish bench 2>&1 >/dev/null | grep 'Nodes searched'
+  - make clean && make build ARCH=x86-64 && ./stockfish bench 2>&1 >/dev/null | grep 'Nodes searched' | tee bench1
+  - make clean && make build ARCH=x86-32 && ./stockfish bench 2>&1 >/dev/null | grep 'Nodes searched' | tee bench2
+  - echo "Checking for same bench numbers..."
+  - diff bench1 bench2 > result
+  - test ! -s result

src/Makefile

@@ -197,6 +197,11 @@ ifeq ($(UNAME),Darwin)
 	LDFLAGS += -arch $(arch) -mmacosx-version-min=10.9
 endif
 
+### Travis CI script uses COMPILER to overwrite CXX
+ifdef COMPILER
+	CXX=$(COMPILER)
+endif
+
 ### On mingw use Windows threads, otherwise POSIX
 ifneq ($(comp),mingw)
 	# On Android Bionic's C library comes with its own pthread implementation bundled in