Log Message:
+ Remove modifications to configure.in and configure in patch-aa and
  patch-ac that altered the order in which the terminal library for
  readline was detected.  The termcap.buildlink3.mk file (included
  indirectly by readline/buildlink3.mk) will do the right thing by
  itself.

+ Modify the pkg-index.tmpl INSTALL script fragment: we can just use
  ${PKG_PREFIX} instead of substituting for @PREFIX@ everywhere.  Also
  refactor the commands to rebuild the package index into a shell
  function and give some indication to the user what is happening.

+ Remove chown operation in post-install that was basically
  cargo-culted from the very first version of R imported into pkgsrc.
  It's not necessary.

+ Support user-destdir installation.

Bump the PKGREVISION to 2.