feat: translate function-like C macros to Rust const fn

Add `--translate-function-macros` flag that translates C function-like
preprocessor macros into Rust `const fn` declarations. This addresses
#753.

- Arithmetic, bitwise, shift, and comparison operators
- Ternary (`? :`) → Rust `if`/`else`
- `sizeof(T)` → `core::mem::size_of::<T>()` with generic type params
- C-style keyword casts: `(int)(x)` → `(x) as i32 as vt`
- Cast with unary prefix: `(int)-1` → `(-1) as i32 as vt`
- Cross-macro calls with automatic turbofish for type params
- Forward references between macros (fixpoint multi-wave resolution)
- Logical NOT `!` with correct C semantics (0→1, nonzero→0)
- Logical AND `&&` / OR `||` with per-operand `!= 0` wrapping
- Float literal inference (including exponent notation like `1e3`)
- Octal literal conversion (`0644` → `0o644`)
- C literal suffix stripping (U/UL/ULL/LU/LLU/f/F and MSVC i64/ui64)
- Suffix-aware unsigned type inference (U→u32, UL/ULL→u64, with C
  promotion for values exceeding u32::MAX)
- Target-aware `long`/`unsigned long` mapping
- Type inference from referenced object-like macro constants
- `func_macro_type` callback for type override
- Allowlist/blocklist filtering matching bindgen's var semantics
- `#undef`/redefine: last definition wins

Variadic macros, `#`/`##`, pointer types, statement macros, `typeof`,
typedef casts `(my_type)(x)`, compiler builtins (`__asm__`,
`__builtin_*`), string literals, assignment operators, comma operator,
address-of `&`, references to non-const globals (`static mut`), and
macros with arity mismatches in cross-macro calls.

1. Unknown identifiers (e.g., enum constants not in the macro constant
   map) are emitted with a cast — works if the identifier exists in
   the generated output, fails otherwise.
2. Unsigned literal suffix (U/ULL) forces u64 when the value exceeds
   u32::MAX, even if a narrower unsigned type would suffice.
3. Float inference is greedy: one float literal forces the entire macro
   to f64. Macros mixing floats with bitwise/modulo/shift are skipped.
4. sizeof-only macros (no constant refs) default to i64; callers cast
   the result.

Author: zRedShift