Disable optimization for wrenPinObj and wrenUnpinObj functions under Microsoft Visual Studio 2013 to prevent the compiler from incorrectly inlining them, which triggers a memory access violation. The pragma directives bracket only these two functions to minimize the impact on the rest of the compilation unit.
Add MSVC 2013 project scaffolding under project/msvc2013/ including wren.sln solution file, wren.vcxproj with Debug/Release Win32 configurations using v120 toolset, and wren.vcxproj.filters organizing source and header files from ../src/ into Visual Studio filter categories.
Enforce a consistent include ordering convention across the codebase: wren_common.h (as configuration header) first, followed by the module's own header, then other wren_*.h headers in lexicographic order, and finally standard library includes. Also add missing wren_common.h include to main.c and wren_io.c, and add _CRT_SECURE_NO_WARNINGS define for MSVC in wren_common.h.
The WREN_COMPUTED_GOTO macro is now conditionally set to 0 when
compiling with _MSC_VER, as Microsoft's compiler does not support
the computed-goto extension used by the VM dispatch loop.
In `src/wren_value.h`, change three flexible array members (`char value[]`, `Upvalue* upvalues[]`, `Value fields[]`) to explicit zero-sized arrays (`char value[0]`, `Upvalue* upvalues[0]`, `Value fields[0]`) to resolve compiler warnings about non-standard zero-sized array usage in structs `ObjString`, `ObjClosure`, and `ObjInstance`.
Marco Lizza