Add foreign static eval(source) method to Meta class in meta.wren and implement wrenBindMetaForeignMethod in wren_meta.c to handle its binding. Change the implicit module name from "main" to "core" in wren_vm.c and restrict foreign method lookup to only the "core" module, enabling Meta foreign methods to be resolved alongside IO methods. Relax the IO foreign method binder to return NULL instead of asserting for non-IO classes, allowing fallback to other library binders.
Add wren_meta.c and wren_meta.h file references to the Xcode project.pbxproj, including the wren_meta.c source in the PBXBuildFile section and both files in the PBXFileReference section. Also reformat indentation in metaEval function body and add a TODO comment for argument type checking.
