Patch for <features.h> comments

[Daniel Jacobowitz]

While looking through <features.h> I got a bit confused by the comments
at the top, and cleaned them up a little.  Is this correct?

Dan

/--------------------------------\  /--------------------------------\
|       Daniel Jacobowitz        |__|        SCS Class of 2002       |
|   Debian GNU/Linux Developer    __    Carnegie Mellon University   |
|         dan@debian.org         |  |       dmj+@andrew.cmu.edu      |
\--------------------------------/  \--------------------------------/