#482346 by Berdir: Move module installation logic to module_enable() to prevent errors upon enabling modules.

- Patch #202775 by michaelfavia, jabapyth: fixed database testing and error handling during installation.

- Patch #210876 by deekayen: log enabling and disabling of modules, and wrote a handy assertLogMessage() function to assert watchdog messages.

- Patch #254491 by chx, catch, justinrandell, pwolanin, David_Rothstein, et al: centralized static caching to improve testability of the Drupal code, and to remove $reset-parameters.  Thanks for taking the time to convince me, catch!

#304163 by chx: Allow update.php to re-generate settings.php. Now possible to upgrade Drupal 6 to Drupal 7. Oh, yeah.

- Patch #361683by Barry, Yves, Karen, Moshe Weitzman, David Strauss, floriant, chx, David Rothstein: initial field API patch. More work to be done, but ... oh my!

#310863 by bangpound, dboulet, and catch: Stop locale module from auto-installing with custom install profiles.

#340500 by justinrandell: Fix silliness in install.inc that was loading the db system twice for no apparent reason.

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

#74645 follow-up by maartenvg: One very important file_scan_directory() call got missed; now HEAD installs again. W00t. ;)

#253569 by aaron, agentrickard, and Dave Reid: Add hook_modules_X to allow modules to react when other modules are enabled, disabled, installed, or uninstalled.

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

- Patch #246143 by bjaspan, Damien Tournoud: make sure updates are run in numeric order, not in definition order.

  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 #245504 by catch, David_Rothstein, Freso, et al: removed the throttle module from Drupal core.

- 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 #217803 by csevb10 and senpai: uninstall system does not correctly remove dynamic menu items when a module is deleted.