Updates for Travis testing where the default Xcode changed from 6.1 to 7.3

See https://blog.travis-ci.com/2016-10-04-osx-73-default-image-live/

.travis.yml

@@ -151,10 +151,9 @@ matrix:
       env: SWIGLANG=python SWIG_CC=gcc-6 SWIG_CXX=g++-6 CPP14=1
       sudo: required
       dist: trusty
-  allow_failures:
-    # Turn off osx testing to fix numerous problems due to default xcode change from 6.1 to 7.3
-    - os: osx
-      env: SWIGLANG= SWIG_CC=gcc-4.2 SWIG_CXX=g++-4.2
+    - compiler: gcc
+      os: osx
+      env: SWIGLANG=
     - compiler: clang
       os: osx
       env: SWIGLANG=
@@ -192,6 +191,7 @@ matrix:
       os: osx
       env: SWIGLANG=tcl
 
+  allow_failures:
     # Lots of failing tests currently
     - compiler: gcc
       os: linux

Tools/travis-osx-install.sh

@@ -5,14 +5,14 @@ set -e # exit on failure
 sw_vers
 brew update
 brew list
-brew install pcre
+# brew install pcre # Travis Xcode-7.3 has pcre
 # brew install boost
 
 WITHLANG=$SWIGLANG
 
 case "$SWIGLANG" in
 	"csharp")
-		brew install https://s3.amazonaws.com/travisbuilds.swig.org/mono.rb
+		brew install mono
 		;;
 	"guile")
 		Tools/brew-install guile