Problem:    Directly checking 'buftype' value.
Solution:   Add the bt_normal() function. (Yegappan Lakshmanan)

Problem:    Difficult to make a plugin that feeds a line to a job.
Solution:   Add the nitial code for the "prompt" buftype.

Problem:    :argedit does not reuse an empty unnamed buffer.
Solution:   Add the BLN_CURBUF flag and fix all the side effects. (Christian
            Brabandt, closes #2713)

Problem:    Using :wqa exits even if a job runs in a terminal window. (Jason
            Felice)
Solution:   Check if a terminal has a running job. (closes #2654)

Problem:    Get "no write since last change" error in terminal window.
Solution:   Use another message when closing a terminal window. Make ":quit!"
            also end the job.

Problem:    There may be side effects when a channel appends to a buffer that
            is not the current buffer.
Solution:   Properly switch to another buffer before appending. (Yasuhiro
            Matsumoto, closes #1926, closes #1937)

Problem:    Using freed memory in quickfix code. (Dominique Pelle)
Solution:   Handle a help window differently. (Yegappan Lakshmanan)

Problem:    Function prototypes missing without the quickfix feature. (Tony
            Mechelynck)
Solution:   Move non-quickfix functions to buffer.c.

Problem:    More buf_valid() calls can be optimized.
Solution:   Use bufref_valid() instead.

Problem:    buf_valid() can be slow when there are many buffers.
Solution:   Add bufref_valid(), only go through the buffer list when a buffer
            was freed.