configure script of "macports" should not link against "/usr/local/"

[markd at macports.org]

Could someone with more programming skills than I comment on this ticket? 
A user thinks there should be a global fix to the problem we have with a
manually installed readline.  I think this must be done on a case-by-case
basis.  Am I missing something?

http://trac.macports.org/projects/macports/ticket/12041

Mark