patch 7.4.1829

Problem:    No message on channel log when buffer was freed.
Solution:   Log a message.

patch 7.4.1828

Problem:    May try to access buffer that's already freed.
Solution:   When freeing a buffer remove it from any channel.

patch 7.4.1827

Problem:    No error when invoking a callback when it's not safe.
Solution:   Add an error message.  Avoid the error when freeing a channel.

patch 7.4.1826

Problem:    Callbacks are invoked when it's not safe. (Andrew Stewart)
Solution:   When a channel is to be closed don't invoke callbacks right away,
            wait for a safe moment.

patch 7.4.1825

Problem:    When job writes to buffer nothing is written. (Nicola)
Solution:   Do not discard a channel before writing is done.

patch 7.4.1824

Problem:    When a job is no longer referenced and does not have an exit
            callback the process may hang around in defunc state. (Nicola)
Solution:   Call job_status() if the job is running and won't get freed
            because it might still be useful.

patch 7.4.1823

Problem:    Warning from 64 bit compiler.
Solution:   Add type cast. (Mike Williams)

patch 7.4.1822

Problem:    Redirecting stdout of a channel to "null" doesn't work. (Nicola)
Solution:   Correct the file descriptor number.

patch 7.4.1821

Problem:    Test fails on MS-Windows.
Solution:   Sort the completion results.

patch 7.4.1820

Problem:    Removing language from help tags too often.
Solution:   Only remove @en when not needed. (Hirohito Higashi)