probleme number 1 :

- configure can find the library readline , but don't
  find the header file . so in this case we don't use lib readline
  .

probleme number 2 :

- when you have postgres 6.2.1 and readline installed
  with the same prefix( and generally all your software ) .  you
  can compile the version 6.3 .  I use this prefix , when configure
  ask me for "Additional directories to search for include files"
  .

  ( because there a conflict in the header when you
    compile psql.c ) In this case, you must permut the sequence of
  directive -I .

Erwan MAS