Fix preprocessor infinite loop with self-referencing object-like macros

[Copilot]

#define FOO FOO causes the preprocessor to loop forever. The non-parameterized macro expansion path lacked the recursion guard that the parameterized path already had.

Changes

• CLanguage/Parser/Preprocessor.cs: Apply the same expansion pattern used for parameterized macros to object-like macros: pre-process the body with the macro's own name removed from defines, then advance i past the inserted tokens. anotherIterationNeeded is not set since the inner loop already handles chain expansion.

• CLanguageTests/PreprocessorTests.cs: Add tests for self-referencing defines (#define FOO FOO), mutual recursion (#define A B / #define B A), chain expansion (#define X Y / #define Y 42), and self-reference in expressions.

Before/after

// Before: blindly re-inserts body, outer loop retries forever
tokens.RemoveAt(i);
tokens.InsertRange(i, define.Body);

// After: expand body with self-reference removed, skip past result
var newBody = define.Body.ToList();
var newDefines = new Dictionary<string, Define>(defines);
newDefines.Remove(define.Name);
while (PreprocessIteration(newDefines, include, newBody, report)) { }
tokens.RemoveAt(i);
tokens.InsertRange(i, newBody);
i += newBody.Count;