Issue #2174353 by anemes, bryanlburkholder: Fix up docs for system_retrieve_file
Issue #2183461 by siliconmeadow: Fix reference to nonexistent function in taxonomy docs
Issue #1948566 by joachim: Document batch API callbacks using new standard
Merge branch '7.x' into 7.x-pimple
use composer autoload in statistics ajax front controller.
Merge branch '7.x-pimple' into 7.x-autoload