Fix the generated C++ for Xcode 10.2

Fixes https://github.com/mono/CppSharp/issues/1203

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

.travis.yml

@@ -5,6 +5,8 @@ os:
   - linux
   - osx
 
+osx_image: xcode10.2
+
 dist: xenial
 
 addons:

src/CppParser/Bindings/CSharp/i686-apple-darwin12.4.0/Std-symbols.cpp

@@ -1,4 +1,5 @@
 #define _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
+#define _LIBCPP_HIDE_FROM_ABI
 
 #include <string>
 

src/CppParser/Bindings/CSharp/i686-pc-win32-msvc/Std-symbols.cpp

@@ -1,4 +1,5 @@
 #define _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
+#define _LIBCPP_HIDE_FROM_ABI
 
 #include <string>
 

src/CppParser/Bindings/CSharp/x86_64-apple-darwin12.4.0/Std-symbols.cpp

@@ -1,4 +1,5 @@
 #define _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
+#define _LIBCPP_HIDE_FROM_ABI
 
 #include <string>
 

src/CppParser/Bindings/CSharp/x86_64-linux-gnu-cxx11abi/Std-symbols.cpp

@@ -1,4 +1,5 @@
 #define _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
+#define _LIBCPP_HIDE_FROM_ABI
 
 #include <string>
 

src/CppParser/Bindings/CSharp/x86_64-linux-gnu/Std-symbols.cpp

@@ -1,4 +1,5 @@
 #define _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
+#define _LIBCPP_HIDE_FROM_ABI
 
 #include <string>
 

src/CppParser/Bindings/CSharp/x86_64-pc-win32-msvc/Std-symbols.cpp

@@ -1,4 +1,5 @@
 #define _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
+#define _LIBCPP_HIDE_FROM_ABI
 
 #include <string>
 

src/Generator/Passes/SymbolsCodeGenerator.cs

@@ -21,6 +21,7 @@ namespace CppSharp.Passes
         public override void Process()
         {
             WriteLine("#define _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS");
+            WriteLine("#define _LIBCPP_HIDE_FROM_ABI");
             NewLine();
 
             if (TranslationUnit.Module == Options.SystemModule)