Fix storage of illegal_names. Add an upgrade routine to fix bad values.

props SergeyBiryukov.
see #23418.
for trunk.



git-svn-id: http://core.svn.wordpress.org/trunk@24448 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Compress scripts/styles: 3.6-beta3-24450.

git-svn-id: http://core.svn.wordpress.org/trunk@24450 1a063a9b-81f0-0310-95a4-ce76da25c4cd