Fix the help text in 'configure'.
Fix the help text in 'configure'.

Reported by Johannes Fahrenkrug <jfa@gebeco.de>.

* configure.in: Change the advertised option name for experimental libtool
  support from '--experimental-libtool' to '--enable-experimental-libtool'.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion