Cleaning up INSTALL before 1.5.6

AFAICS, there's a couple of things that should be changed in the list of 
system requirements:

- cpio is no longer needed due to git-clone now being a builtin

- According to some other thread on this list, curl might no longer be 
needed, as all its users are now builtin, and uses libcurl instead.


Have fun! :)

...Johan

-- 
Johan Herland, [off-list ref]
www.herland.net