Feature: Support nested macros in cc45 preprocessor

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Feature Request

Component: cc45 (C Compiler Preprocessor) / cp45 (Preprocessor)

Description:
Add support for nested macro definitions and invocations in the cc45 C preprocessor.

Currently, the cc45 preprocessor supports standard C preprocessor macros, but does not reliably handle macros defined within other macros (nested macro definitions) or complex multi-level macro invocations.

Use Case:
Complex C codebases benefit from hierarchical macro abstractions for:

• Building library macros that compose smaller utility macros
• Parameterized code generation at multiple levels
• Conditional compilation strategies that depend on macro nesting

Example Desired Syntax:

#define BASE_SETUP() \
  do { \
    asm volatile("pha"); \
    asm volatile("phx"); \
  } while(0)

#define FULL_SETUP(flag) \
  do { \
    BASE_SETUP(); \
    if (flag) { \
      asm volatile("phy"); \
    } \
  } while(0)

Implementation Considerations:

• Ensure proper macro argument expansion at each nesting level
• Handle edge cases with stringification (#) and token pasting (##) in nested macros
• Prevent infinite recursion with nesting depth limits or cycle detection
• Maintain compatibility with C99/C11 preprocessor standards
• Consider performance impact on preprocessing time
• Test compatibility with GCC and Clang preprocessor behavior

Related Documentation:

• doc/cc45.md — Compiler documentation
• doc/cp45.md — Preprocessor features

Priority: Medium (code organization improvement)