doc about linking in the x86_64 linux environment

to nvidia guys:

in the x86_64 linux environment, both glut lib for i386 arch, freeglut-2.2.0-14.i386 and that for x86_64, freeglut-2.2.0-14.x86_64 are installed, and building some CUDA SDK projects using OpenGL needs a link to under /usr/lib64/ dir, not /usr/lib/. there will be a error, “/usr/bin/ld: skipping incompatible /usr/lib/ when searching for -lglut/usr/bin/ld: cannot find -lglut” coming out when you build the SDK projects, if you have added a link according to Software Development Kit(CUDA SDK) Release Notes Version 2.1 for Linux because the added link points at under /usr/lib/. i think it is convenient for the SDK users if you distinguish x86_64 from i386 on this issue in your doc. :)