Add Visual Studio 2013 solution and project files under project/msvc2013/ directory, enabling native Windows builds without MinGW. Include Marco Lizza in AUTHORS for the contribution. Fix C89 compatibility issues for MSVC: disable computed goto via _MSC_VER check, define inline as _inline for non-C++ mode, change flexible array members from empty brackets to [0] syntax, and fix char to int type for readHexDigit return value. Refactor single-line if/while/for bodies in wren_compiler.c to use braces to satisfy MSVC stricter parsing.
Bob Nystrom
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