Fix dist/nightly.sh for pre-1.7 Subversions.
Fix dist/nightly.sh for pre-1.7 Subversions.

* tools/dist/nightly.sh: Avoid using the 'svn export $file $dir' syntax.

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