Attempt to fix Travis build

.travis.yml

@@ -47,7 +47,7 @@ before_install:
     - if [ "$BUILD" == "C++14 -O2" ]; then export WML_TEST_TIME=15; fi
     - if [ "$BUILD" == "C++14 -O2" ]; then export CXXSTD="1y"; fi
 
-    - if [ "$BUILD" == "-O0" ]; then export EXTRA_FLAGS_RELEASE="-O0 -Wno-literal-suffix -Wno-deprecated-declarations"; fi
+    - if [ "$BUILD" == "-O0" ]; then export EXTRA_FLAGS_RELEASE="-O0 -Wno-deprecated-declarations"; fi
     - if [[ "$BUILD" == "-O0" ]] && [[ "$CXX" == "clang++" ]]; then export EXTRA_FLAGS_RELEASE="-O0 -Wno-literal-suffix -Wno-deprecated-declarations -Wno-deprecated-register"; fi
     - if [ "$BUILD" == "-O0" ]; then export PLAY_TEST=false; fi
     - if [ "$BUILD" == "-O0" ]; then export MP_TEST=false; fi

src/utils/functional.hpp

@@ -27,8 +27,10 @@
 // Instead, we specialize std::is_placeholder for the Boost placeholders,
 // so that Boost placeholders can be passed to std::bind.
 
-template<int N>
-struct std::is_placeholder<boost::arg<N>> : public std::integral_constant<int, N> {};
+namespace std { // Some compilers can't handle it being specialized in the global scope
+	template<int N>
+	struct is_placeholder<boost::arg<N>> : public integral_constant<int, N> {};
+}
 
 namespace detail {
 	template<typename Ret, typename... T>