MSVC build fixes

cmake/GtsamBuildTypes.cmake

@@ -81,6 +81,11 @@ if(MSVC)
     WINDOWS_LEAN_AND_MEAN
     NOMINMAX
 	)
+  # Avoid literally hundreds to thousands of warnings:
+  list_append_cache(GTSAM_COMPILE_OPTIONS_PUBLIC
+	/wd4267 # warning C4267: 'initializing': conversion from 'size_t' to 'int', possible loss of data
+  )
+
 endif()
 
 # Other (non-preprocessor macros) compiler flags:

gtsam/nonlinear/Values-inl.h

@@ -348,7 +348,9 @@ namespace gtsam {
        throw ValuesKeyDoesNotExist("at", j);
 
     // Check the type and throw exception if incorrect
-    return internal::handle<ValueType>()(j,item->second);
+    // h() split in two lines to avoid internal compiler error (MSVC2017)
+    auto h = internal::handle<ValueType>();
+    return h(j,item->second);
   }
 
   /* ************************************************************************* */