#551658 follow-up by pwolanin: Revert back to D6-style temporary folder logic to avoid various platform issues.

- Patch #743908 by David_Rothstein, casey, Gábor Hojtsy: skip overlay initialization if already done.

- Patch #768040 by jhodgdon, janusman, codycraven: truncate_utf8() only works for latin languages and drupal_substr() had a bug.

- Patch #520760 by sun, Berdir, Steven Merrill, David_Rothstein, Heine, duellj, catch: fixed SA-CORE-2009-007 user signature format.

- Patch #663126 by casey, seutje: active items in top level IA don't have the light gray background when overlay is enabled.

#799982 by tstoeckler, StuartJNCC: Fixed Updating D6 -> D7 fails if the D6 site has Date module applied.

#680992 by Berdir, catch, andypost, douggreen, mr.baileys: Fixed comments are added to search index without checking access.

#668640 by casey, aspilicious, et al: Re-implement Overlay without jQuery UI Dialog; massive performance improvement, helps address several critical issues.

#794184 by JacobSingh, catch, chx: Fixed contact_update_7002() fails when the contact module is not enabled.

#797024 follow-up by justinrandell: Remove critical performance regression due to stale file time values.

#797024 by pwolanin, justinrandell: Fixed Moving a class between files can cause SQL errors on registry rebuild.

- Patch #803212 by effulgentsia, Heine: protection against forgery of input selection value doesn't work with checkboxes.

- Patch #807396 by Berdir, carlos8f, David_Rothstein: database errors not displaying during install.