#19 More standard installation layout

[Jason Long]

Currently, installing with --prefix=/usr/local/dkimproxy is recommended since it puts some files in $prefix/lib which might clobber other files.
I want to change things so that --prefix=/usr/local can be the default,
and the library files will be stored in /usr/local/lib/dkimproxy or something like that.

(This will make the man pages I'm working on show up at the right spot.)