HACKING.md: explain C platform macros from https://cfengine.com/dev/issues/2018
Redmine#3429: acceptance test for copy and purge of empty directory
Fix misspelling of daemon
Fix misspelling of Commercial in 607 places
Fix misspelling of available in libutils/man.c
Fix misspelling of overridden in one place
Merge pull request #1022 from tzz/feature/2018-explain-platform-macros

HACKING.md: explain C platform macros from https://cfengine.com/dev/issues/2018
Add acceptance test for empty splice dereference
Merge pull request #1024 from bahamat/master

Fix some spelling mistakes.
Merge pull request #1023 from tzz/tzz/3429-copy-and-purge

Redmine#3429: acceptance test for copy and purge of empty directory
per tzz's suggestion in https://github.com/cfengine/core/pull/1028#issuecomment-26712272