Issue #1260932 by DjebbZ, pwolanin: hook_nodeapi() optional arguments should not be made required by some core modules either

Issue #321063 by eMPee584, Kars-T, pillarsdotnet: Path book/export/html/N with a non-book nid should abort and return 404 not found.

#203323 by JirkaRybka, robertgarrigos, lilou, thePanz, c960657, sun: move the LANGUAGE_* constants to bootstrap.inc and remove several defined() checks on them now that they are always defined

#272900 by pwolanin: avoid saving book (menu) data when another user changed the book in the meantime

#231587 by pwolanin, killes: (performance) use two level cache in menus, instead of storing very large amounts of data multiple times

#181125 follow up by beginner: book.js should have been removed earlier in #181125, was a commit mistake

#205075 report by ktabuer, patch by myself, testing by ktauber and Lynn: book block throws notice when used on non-book-node page (with a little bit of code cleanup)

#202425 by keith.smith: standardize reference to block placement page as 'blocks administration page' to avoid any confusion

#199336 by JirkaRybka: remove improper t() use in update code (update goes all in English, but there were some mistakes), and add messages to updates where there was no return value otherwise, so users know what happens in each update

- Patch #164532 by catch, pwolanin, David Strauss, et al.: improve table indicies for common queries.

#200069 by keith.smith: new standard for 'more information' links in module help texts, as the handbook we referred to before was renamed

#197297 by DanW (as GHOP 17), and keith.smith: clean up lots of help texts, update to drag and drop functionality, drupal.module removal, etc

 - whitespaces at end of lines
 - indentation
 - control structure usage
 - whitespace in empty lines
 - phpdoc comment formatting

- Patch #163246 by keith smith, freso, O Govinda, catch, webchick et al: fixed minor spelling issues and fixed spacing issues.

#191360 by chx: allow contributed modules to override the book and menu parent selectors (to improve usability and performance)

 - book outline form reordering in real-time
 - better context sensitive book parent editing