#147000 by pwolanin, mikeytown2, et. al.: avoid multiple, parallel rebuildings of module and theme data

#275796 by Gribnif, Damien Tournoud, Dave Reid, vaish: module_list() should set its static variable to NULL instead of unset()-ing it, so it does not retain its value

#194010 by chx: Proper recursive dependency checking and ordering module installation in dependency order, so later installed modules can use previously installed module functionality

 - possible timeouts with installing/enabling lots of modules at once in core
 - enable install profiles to have more modules without fear of timeouts on install
 - bootstrap Drupal before each module load, so previously enabled modules are bootstrapped
 - let modules run their hook_requirements() (although actually calling them will be possibly fixed in another patch)

#151868 by chx: avoid using array_shift() because it takes a lot of time to rehash the array, so indexing the array is more performant, then shifting items one by one

#166593 by hswong3i: move literal values out of some core queries to support cross-database compatibility (ie. better SQL parsing and altering options)

#154949 by Crell and dww: let modules and themes specify a minimum required PHP version, under which they will not be possible to be turned on

- Patch #63881 by kbahey and jakeg: improved Drupal's logging functionality.  Added support for external loggers, and included a small syslog module into core.

- Patch #34755 by chx et al: faster menu system.  HEAD is temporary broken and there is no upgrade path yet.

- Patch #101379 by ChrisKennedy, neclimdul et al: modules missing .info files wrongly adding empty entries to module page.

- Patch #88287 by asimmonds, dww et al: installer doesn't support modules outside root/modules directory.  Critical bugfix.

- Patch #81740 by merlinofchaos, webchick, moshe, neclimdul et al: added package support to the modules page.