VS2008 build issue with protobuf 3.5.0

[jakirkham]

Ran into the following issue when trying to build protobuf 3.5.0 where map::at was used. The map::at method only exists in C++11. As such it cannot compile with a non-C++11 compiler like VS2008.

C:\bld\protobuf_1513642428254\work\protobuf-3.5.0\src\google\protobuf\util\field_mask_util.cc(377) : error C2039: 'at' : is not a member of 'std::map<_Kty,_Ty>'
        with
        [
            _Kty=std::string,
            _Ty=google::protobuf::util::`anonymous-namespace'::FieldMaskTree::Node *
        ]
NMAKE : fatal error U1077: 'C:\PROGRA~2\MICROS~1.0\VC\bin\cl.exe' : return code '0x2'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\BIN\nmake.exe"' : return code '0x2'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\BIN\nmake.exe"' : return code '0x2'
Stop.

ref: https://ci.appveyor.com/project/conda-forge/protobuf-feedstock/build/job/o85bad6hfjhvyxvu

[xfxyjwf]

We will release 3.5.1 very soon. Could you help make a pull request to fix this in the 3.5.x branch?

@pherl is working on 3.5.1 release.

[jakirkham]

PR ( #4074 ) fixed this issue.

[jakirkham]

Should add that when trying to build protobuf with that patch ran into issue ( #4075 ).