Fix MSVC build errors

[jlblancoc]

Please, find some fixes trying to make GTSAM/develop to build under MSVC2017 again.

Pay special attention to this commit. It was required to fix the following error. After unrolling the stack of template instantiations, I think the change makes (sort of) sense...

1>D:\code\gtsam\gtsam\gtsam/base/GenericValue.h(171): error C2678: binary '=': no operator found which takes a left-hand operand of type 'const gtsam::Cal3_S2' (or there is no acceptable conversion)
1>D:\code\gtsam\gtsam\gtsam/geometry/Cal3_S2.h(234): note: could be 'gtsam::Cal3_S2 &gtsam::Cal3_S2::operator =(gtsam::Cal3_S2 &&)'
1>D:\code\gtsam\gtsam\gtsam/geometry/Cal3_S2.h(234): note: or       'gtsam::Cal3_S2 &gtsam::Cal3_S2::operator =(const gtsam::Cal3_S2 &)'
1>D:\code\gtsam\gtsam\gtsam/base/GenericValue.h(171): note: while trying to match the argument list '(const gtsam::Cal3_S2, const gtsam::Cal3_S2)'
1>D:\code\gtsam\gtsam\gtsam/base/GenericValue.h(169): note: while compiling class template member function 'gtsam::GenericValue<ValueType> &gtsam::GenericValue<ValueType>::operator =(const gtsam::GenericValue<ValueType> &)'
1>        with
1>        [
1>            ValueType=gtsam::Cal3_S2
1>        ]
1>D:\code\gtsam\gtsam\gtsam/base/GenericValue.h(161): note: see reference to function template instantiation 'gtsam::GenericValue<ValueType> &gtsam::GenericValue<ValueType>::operator =(const gtsam::GenericValue<ValueType> &)' being compiled
1>        with
1>        [
1>            ValueType=gtsam::Cal3_S2
1>        ]
1>D:\code\gtsam\gtsam\gtsam/nonlinear/Values-inl.h(67): note: see reference to class template instantiation 'gtsam::GenericValue<ValueType>' being compiled
1>        with
1>        [
1>            ValueType=gtsam::Cal3_S2
1>        ]
1>D:\code\gtsam\gtsam\gtsam/nonlinear/Values-inl.h(63): note: while compiling class template member function 'gtsam::_ValuesConstKeyValuePair<ValueType> gtsam::ValuesCastHelper<const ValueType,gtsam::_ValuesConstKeyValuePair<ValueType>,gtsam::Values::ConstKeyValuePair>::cast(KeyValuePairType)'
1>        with
1>        [
1>            ValueType=gtsam::Cal3_S2,
1>            KeyValuePairType=gtsam::Values::ConstKeyValuePair
1>        ]
1>D:\code\gtsam\gtsam\gtsam/nonlinear/Values-inl.h(143): note: see reference to function template instantiation 'gtsam::_ValuesConstKeyValuePair<ValueType> gtsam::ValuesCastHelper<const ValueType,gtsam::_ValuesConstKeyValuePair<ValueType>,gtsam::Values::ConstKeyValuePair>::cast(KeyValuePairType)' being compiled
1>        with
1>        [
1>            ValueType=gtsam::Cal3_S2,
1>            KeyValuePairType=gtsam::Values::ConstKeyValuePair
1>        ]
1>D:\code\gtsam\gtsam\gtsam/nonlinear/Values-inl.h(149): note: see reference to class template instantiation 'gtsam::ValuesCastHelper<const ValueType,gtsam::_ValuesConstKeyValuePair<ValueType>,gtsam::Values::ConstKeyValuePair>' being compiled
1>        with
1>        [
1>            ValueType=gtsam::Cal3_S2
1>        ]
1>D:\code\gtsam\gtsam\gtsam/nonlinear/Values-inl.h(134): note: while compiling class template member function 'gtsam::Values::Filtered<gtsam::Cal3_S2>::Filtered(const boost::function<bool (const gtsam::Values::ConstKeyValuePair &)> &,gtsam::Values &)'
1>D:\code\gtsam\gtsam\gtsam/nonlinear/Values-inl.h(245): note: see reference to function template instantiation 'gtsam::Values::Filtered<gtsam::Cal3_S2>::Filtered(const boost::function<bool (const gtsam::Values::ConstKeyValuePair &)> &,gtsam::Values &)' being compiled
1>D:\code\gtsam\gtsam\gtsam_unstable\examples\ConcurrentCalibration.cpp(149): note: see reference to class template instantiation 'gtsam::Values::Filtered<gtsam::Cal3_S2>' being compiled
1>C:\local\boost_1_64_0\boost/bind/placeholders.hpp(54): note: see reference to class template instantiation 'boost::arg<9>' being compiled
1>C:\local\boost_1_64_0\boost/bind/placeholders.hpp(53): note: see reference to class template instantiation 'boost::arg<8>' being compiled
1>C:\local\boost_1_64_0\boost/bind/placeholders.hpp(52): note: see reference to class template instantiation 'boost::arg<7>' being compiled
1>C:\local\boost_1_64_0\boost/bind/placeholders.hpp(51): note: see reference to class template instantiation 'boost::arg<6>' being compiled
1>C:\local\boost_1_64_0\boost/bind/placeholders.hpp(50): note: see reference to class template instantiation 'boost::arg<5>' being compiled
1>C:\local\boost_1_64_0\boost/bind/placeholders.hpp(49): note: see reference to class template instantiation 'boost::arg<4>' being compiled
1>C:\local\boost_1_64_0\boost/bind/placeholders.hpp(48): note: see reference to class template instantiation 'boost::arg<3>' being compiled
1>C:\local\boost_1_64_0\boost/bind/placeholders.hpp(47): note: see reference to class template instantiation 'boost::arg<2>' being compiled
1>C:\local\boost_1_64_0\boost/bind/placeholders.hpp(46): note: see reference to class template instantiation 'boost::arg<1>' being compiled
1>Done building project "ConcurrentCalibration.vcxproj" -- FAILED.

[dellaert]

Excellent, glad to know it compiles with so little changes. Would be nice if we could add windows to CI, but boost is not among packages installed in early version: https://docs.travis-ci.com/user/reference/windows/

[dellaert]

Feel free to merge and then rebase other one...