Don't #define snprintf in VS 2015 or higher.
In VS 2015 and higher snprintf is supplied and therefore vsnprintf doesn't need to be defined. This also avoids problems caused by _snprintf being different from snprintf. This fixes a build break with VS 2015 and improves security. Originally submitted via chromium by firstname.lastname@example.org https://codereview.chromium.org/1055603003 Additionally break this MSVC-specific tweak to a new file, which will become the home of all such MSVC-specific things. This requires adding a dependency on msvc.h to every example which uses args.c and tools_common.h Change-Id: I35b5f8e7ea00f6627403aabc9ea79b0412557a99