all gcc builds under osx now allowed to fail - I have no $^&%-ing clue why some of them started failing - and in different ways!

see this build - https://travis-ci.org/onqtam/doctest/jobs/166452422
diff --git a/.travis.yml b/.travis.yml
index 0e6df47..2619dc1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -106,7 +106,7 @@
           sources: *apt_sources
 
     # GCC 4.9
-    - env: COMPILER=g++-4.9 HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true # ASAN_32 dropped weird errors when using ASAN_OPTIONS - most probably g++ 4.9 bug
+    - env: COMPILER=g++-4.9 HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true # no ASAN_32 - errors when using ASAN_OPTIONS - probably g++ 4.9 bug
       compiler: gcc
       addons: &gcc49
         apt:
@@ -211,7 +211,7 @@
     # OSX GCC 4.4
     - env: COMPILER=g++-4.4
       compiler: gcc
-      osx_image: beta-xcode6.3
+      osx_image: beta-xcode6.2
       os: osx
 
     # OSX GCC 4.5
@@ -239,7 +239,7 @@
       os: osx
 
     # OSX GCC 4.9
-    - env: COMPILER=g++-4.9 HAS_UBSAN_32=true HAS_UBSAN_64=true # ASAN_32/ASAN_64 dropped weird errors when using ASAN_OPTIONS - probably g++ 4.9 bug
+    - env: COMPILER=g++-4.9 HAS_UBSAN_32=true HAS_UBSAN_64=true # no ASAN_32/ASAN_64 - errors when using ASAN_OPTIONS - probably g++ 4.9 bug
       compiler: gcc
       osx_image: beta-xcode6.3
       os: osx
@@ -262,12 +262,12 @@
       os: osx
 
   allow_failures:
-    # for some reason these builds fail...
+    # for some reason some of these builds fail sometimes...
 
     # OSX GCC 4.4
     - env: COMPILER=g++-4.4
       compiler: gcc
-      osx_image: beta-xcode6.3
+      osx_image: beta-xcode6.2
       os: osx
 
     # OSX GCC 4.5
@@ -294,6 +294,24 @@
       osx_image: beta-xcode6.3
       os: osx
 
+    # OSX GCC 4.9
+    - env: COMPILER=g++-4.9 HAS_UBSAN_32=true HAS_UBSAN_64=true # no ASAN_32/ASAN_64 - errors when using ASAN_OPTIONS - probably g++ 4.9 bug
+      compiler: gcc
+      osx_image: beta-xcode6.3
+      os: osx
+
+    # OSX GCC 5
+    - env: COMPILER=g++-5 HAS_ASAN_32=true HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true
+      compiler: gcc
+      osx_image: beta-xcode6.3
+      os: osx
+
+    # OSX GCC 6
+    - env: COMPILER=g++-6 HAS_ASAN_32=true HAS_UBSAN_32=true HAS_ASAN_64=true HAS_UBSAN_64=true
+      compiler: gcc
+      osx_image: beta-xcode6.3
+      os: osx
+
 before_install:
   - git submodule update --init --recursive
 
@@ -351,7 +369,7 @@
         brew install gcc47
       fi
       if [[ "${COMPILER}" = "g++-4.8" ]]; then
-        brew outdated gcc48 || brew upgrade gcc48
+        brew install gcc48
       fi
       if [[ "${COMPILER}" = "g++-4.9" ]]; then
         brew install gcc49