Travis/OS X: Use 'brew bundle' + Brewfile

This ensures that the build script will not fail if the Homebrew
dependencies are already installed.

.travis.yml

@@ -44,7 +44,7 @@ matrix:
 before_install:
   - if [ "$TRAVIS_OS_NAME" = "osx" ]; then
       brew update &&
-      brew install nasm homebrew/versions/gcc5 md5sha1sum Caskroom/versions/java6 &&
+      brew bundle &&
       ln -fs /usr/local/bin/gpg1 /usr/local/bin/gpg &&
       git clone --depth=1 https://github.com/libjpeg-turbo/gas-preprocessor.git ~/src/gas-preprocessor &&
       ln -fs /Applications/Xcode.app /Applications/Xcode72.app;

Brewfile

@@ -0,0 +1,4 @@
+brew 'nasm'
+brew 'gcc@5'
+brew 'md5sha1sum'
+cask 'Caskroom/versions/java6'

Makefile.am

@@ -174,7 +174,7 @@ EXTRA_DIST = win release $(DOCS) testimages CMakeLists.txt \
 	sharedlib/CMakeLists.txt cmakescripts libjpeg.map.in doc doxygen.config \
 	doxygen-extra.css jccolext.c jdcolext.c jdcol565.c jdmrgext.c jdmrg565.c \
 	jstdhuff.c jdcoefct.h jdmainct.h jdmaster.h jdsample.h \
-	md5/CMakeLists.txt
+	md5/CMakeLists.txt Brewfile
 
 dist-hook:
 	rm -rf `find $(distdir) -name .svn`