title: Autoconf: detecting if target platform is 32-bit or 64-bit
body: <p>In GNU Autoconf: is there an easy way (premade macro? or autoconf-archive macro?) to determine the bitness of our target platform is 32-bit or 64-bit? In case you are curious why I asked this: I need to know this since in the good'old Fortran (pre-2003) there is no way to determine if size_t is 4-byte or 8-byte wide. </p>