Additional features beyond detection

 - Use alternate compilers
   CXX=g++-3.4 ./configure
 - Separate build dirs
   cd ../build-foo
   ../antani-1.0/configure --with-foo
   cd ../build-bar
   ../antani-1.0/configure --with-bar
 - ./configure --prefix=foo
   make install prefix=foo
 - easy to make deb or rpm when a package correctly uses autotools
 
