Compiling Bison with non-GNU compiler

[Lee Kindness]

When compiling Bison 1.29 on AIX 4.3.3 the use of the __attribute__
function of GCC causes the build to fail. This should be conditionally
used if the compiler is GCC. The following patch corrects complain.h:

*** complain.h  Tue Nov  7 16:28:46 2000
--- complain.h  Tue Oct  9 12:29:05 2001
***************
*** 28,44 ****
  /* Informative messages, but we proceed. */
  
  extern void warn (const char *format, ...)
!      __attribute__ ((__format__ (__printf__, 1, 2)));
  
  /* Something bad happen, but let's continue and die later. */
  
  extern void complain (const char *format, ...)
!      __attribute__ ((__format__ (__printf__, 1, 2)));
  
  /* Something bad happen and we die now. */
  
  extern void fatal (const char *format, ...)
!      __attribute__ ((__format__ (__printf__, 1, 2)));
  
  /* Print a message with `fprintf (stderr, FORMAT, ...)';
     if ERRNUM is nonzero, follow it with ": " and strerror (ERRNUM).
--- 28,53 ----
  /* Informative messages, but we proceed. */
  
  extern void warn (const char *format, ...)
! #ifdef __GNUC__
!      __attribute__ ((__format__ (__printf__, 1, 2)))
! #endif
!   ;
  
  /* Something bad happen, but let's continue and die later. */
  
  extern void complain (const char *format, ...)
! #ifdef __GNUC__
!      __attribute__ ((__format__ (__printf__, 1, 2)))
! #endif
!   ;
  
  /* Something bad happen and we die now. */
  
  extern void fatal (const char *format, ...)
! #ifdef __GNUC__
!      __attribute__ ((__format__ (__printf__, 1, 2)))
! #endif
!   ;
  
  /* Print a message with `fprintf (stderr, FORMAT, ...)';
     if ERRNUM is nonzero, follow it with ": " and strerror (ERRNUM).
***************
*** 46,52 ****
  
  extern void error (int status, int errnum,
                   const char *format, ...)
!      __attribute__ ((__format__ (__printf__, 3, 4)));
  
  #else
  void warn ();
--- 55,64 ----
  
  extern void error (int status, int errnum,
                   const char *format, ...)
! #ifdef __GNUC__
!      __attribute__ ((__format__ (__printf__, 3, 4)))
! #endif
!   ;
  
  #else
  void warn ();