Switch to Xcode 11 in Travis CI.
Switch to Xcode 11 in Travis CI.

ddobrev/CppSharp,mono/CppSharp,zillemarco/CppSharp,mono/CppSharp,ddobrev/CppSharp,ddobrev/CppSharp,zillemarco/CppSharp,ddobrev/CppSharp,zillemarco/CppSharp,mono/CppSharp,mono/CppSharp,zillemarco/CppSharp,mono/CppSharp,ddobrev/CppSharp,zillemarco/CppSharp,mono/CppSharp