Fix macOS build failure due to API_DEPRECATED macro conflict

[undici77]

Bug description
On macOS, compilation fails when osdp_export.h is included after system headers (e.g., <os/availability.h>), which defines API_DEPRECATED with a variadic signature. The library’s single-argument macro redefinition causes:

error: too many arguments provided to function-like macro invocation

Expected behavior
The header should be safely re-includable without conflicts, regardless of system header order.

Observed behavior
Macro redefinition error on macOS (Clang/Xcode) due to incompatible API_DEPRECATED definitions.

Fix applied
Added #undef API_DEPRECATED before redefining the macro in osdp_export.h, ensuring safe override of any prior definition (e.g., from Apple’s SDK).

/* ---------- Deprecation (with message) ---------- */

/*
 * CHANGED: Undefine API_DEPRECATED before redefining it. On macOS the SDK
 * header <os/availability.h> defines API_DEPRECATED with a different
 * signature (platform/version specifiers, not a plain string), which causes
 * macro expansion errors when osdp.h uses OSDP_DEPRECATED_EXPORT("msg").
 */
#undef API_DEPRECATED

/* Prefer C++ [[deprecated("msg")]] if available, otherwise compiler specifics. */
#if defined(__cplusplus) && API_HAS_CPP_ATTR(deprecated)
  /* [[deprecated("msg")]] supported */
  #define API_DEPRECATED(msg) [[deprecated(msg)]]
#elif defined(_MSC_VER)
  /* MSVC supports __declspec(deprecated("msg")) */
  #define API_DEPRECATED(msg) __declspec(deprecated(msg))
#elif (defined(__clang__) && API_HAS_ATTR(deprecated)) \
      || (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)))
  /* Clang and modern GCC support attribute deprecated("msg") */
  #define API_DEPRECATED(msg) __attribute__((deprecated(msg)))
#elif (defined(__GNUC__) || defined(__clang__))
  /* Older GCC/Clang: attribute deprecated without message */
  #define API_DEPRECATED(msg) __attribute__((deprecated))
#else
  /* Unknown compiler: no-op */
  #define API_DEPRECATED(msg)
#endif