gnustep-howto documentation update

[Eric Wasylishen]

Hi,

I committed some changes to the gnustep-howto.texi document, updating the 
section on library dependencies, and also suggesting the use of "sudo -E" when 
running make install.

I also noticed that the copy on the web site needs to be regenerated some time:
http://www.gnustep.org/resources/documentation/User/GNUstep/gnustep-howto_3.html

Cheers
Eric