Solution: The Coverity Static Code Analyzer was used on libzmq code and found
many issues with uninitialized member variables, some redefinition of variables
hidding previous instances of same variable name and a couple of functions
where return values were not checked, even though all other occurrences were
checked (e.g. init_size() return).

Solution: Corrected Toolset setting where needed and inprove compilation speed
by adding defintion of WIN32_LEAN_AND_MEAN prior to any Windows specific
include files, which skips non-essential definitions during compilation.

Solution: Corrected Toolset setting where needed and inprove compilation speed
by adding defintion of WIN32_LEAN_AND_MEAN prior to any Windows specific
include files, which skips non-essential definitions during compilation.

There is an option to enable/disable libsodium via the Visual Studio
UI. This is not practical for command-line usage (via msbuild).

Solution: add configure.bat that searches for libsodium in sibling
directory to libzmq; if it finds it, defines HAVE_LIBSODIUM 1.

This is consistent with zproject, which has the same problem and
is getting the same solution for all dependency resolution on
Windows.

Note that this approach also provides a way to support tweetnacl
via a configure option.

Also, removed duplicate props files and re-copy in configure.bat
as it was an insane nightmare to update these by hand. (and not
clear that they were identical. Now it's forced.)

Solution: add Iphlpapi.lib to libraries to link against