#203323 by JirkaRybka, robertgarrigos, thePanz, c960657, and sun: Fix undefined index locale in install.php and clean up crufty code.

- Patch #201122 by c960657, Moshe Weitzman: never write anonymous sessions, unless something has been written to . This is an important performance improvements -- as long as you use modules that use  carefully. It might be good to report some analytics about this in the performance settings page so administrators can see if there is a 'broken' module.

- Patch #352722 by dmitrig01: conditionally show 'settings.php not writable' error so that the message doesn't show up when the file does not exist.

- Patch #333143 by justinrandell: cleaning up the Drupal bootstrap code, removing bootstrap flag in system table.

#11077 by mfb, KarenS, macgirvin, and jjkd: Can you say Daylight Savings Time? I bet you didn't think Drupal ever would! :)

- Patch #74645 by drewish, roychri et al: modify file_scan_directory to use a regex for the nomask (and code clean-up).

- Patch #208793 by kbahey, Damien Tournoud: stop hardcoding the HTTP protocol version where possible.

- Patch #302763 by Dave Reid, Rob Loach: replace time() by ['REQUEST_TIME'] as per Rasmus' suggestion.  Removed drupal_referrer() for consistency.

- Patch #225450 by Crell, chx, bjaspan, catch, swentel, recidive et al: next generation database layer for Drupal 7.

- Patch #252013 by Eaton, pwolanin, Susurrus et al: drupal_render() now printes #markup, not #value.

  et al.  Can you say 'registry'?  Drupal now maintains an internal registry of
  all functions or classes in the system, allowing it to lazy-load code files as
  needed (reducing the amount of code that must be parsed on each request). The
  list of included files is cached per menu callback for subsequent loading by
  the menu router. This way, a given page request will have all the code it needs
  but little else, minimizing time spent parsing unneeded code.

- Patch #245115 by kkaefer, John Morahan, JohnAlbin et al: after a long discussion we've decided to make the concatenation operator consistent with the other operators.

- Patch #209240 by saxofaan, mike stewart, gopherspidey: fixed installation problem with multi-site setups.

#199946 by JirkaRybka: append a short query string to CSS and JS files, changing on upgrades, so on core/module/theme upgrades, browser caches will 'flush'

#197720 by nedjo, scor, keith.smith, catch: inform installing users about PHP memory requirements of Drupal 6