popt: update to 1.18

Replace HOMEPAGE and MASTER_SITE, the old rpm5.org site seems dead & broken

Changes from popt 1.16
  fix an ugly and ancient security issue with popt failing to
    drop privileges on alias exec from a SUID/SGID program
  perform rudimentary sanity checks when reading in popt config files
  collect accumulated misc fixes (memleaks etc) from distros
  convert translations to utf-8 encoding
  convert old postscript documentation to pdf
  dust off ten years worth of autotools sediment
  reorganize and clean up the source tree for clarity
  remove the obnoxious splint annotations from the sources

(tnn)