patch 8.0.0275: the screen may be updated at the wrong time

Problem:    When checking for CTRL-C typed the GUI may detect a screen resize
            and redraw the screen, causing trouble.
Solution:   Set updating_screen in ui_breakcheck().

patch 8.0.0274: possible recursive screen updating causes trouble

Problem:    When update_single_line() is called recursively, or another screen
            update happens while it is busy, errors may occur.
Solution:   Check and update updating_screen. (Christian Brabandt)

patch 8.0.0273: dead code detected by Coverity

Problem:    Dead code detected by Coverity when not using gnome.
Solution:   Rearrange the #ifdefs to avoid dead code.

patch 8.0.0272: crash on exit is not detected when running tests

Problem:    Crash on exit is not detected when running tests.
Solution:   Remove the dash before the command. (Dominique Pelle, closes
            vim#1425)

patch 8.0.0271: may get ml_get error when :tcldo deletes lines

Problem:    May get ml_get error when :tcldo deletes lines or switches to
            another buffer. (Nikolai Pavlov, closes vim#1421)
Solution:   Check the buffer and line every time.

patch 8.0.0270: may get ml_get error when :rubydo deletes lines

Problem:    May get ml_get error when :rubydo deletes lines or switches to
            another buffer. (Nikolai Pavlov, issue vim#1421)
Solution:   Check the buffer and line every time.

patch 8.0.0269: may get ml_get error when :perldo deletes lines

Problem:    May get ml_get error when :perldo deletes lines or switches to
            another buffer. (Nikolai Pavlov, issue vim#1421)
Solution:   Check the buffer and line every time.

patch 8.0.0268: may get ml_get error when :luado deletes lines

Problem:    May get ml_get error when :luado deletes lines or switches to
            another buffer. (Nikolai Pavlov, issue vim#1421)
Solution:   Check the buffer and line every time.

patch 8.0.0267: channel test sometimes fails on Mac

Problem:    A channel test sometimes fails on Mac.
Solution:   Add the test to the list of flaky tests.

patch 8.0.0266: compiler warning for using uninitialized variable

Problem:    Compiler warning for using uninitialized variable.
Solution:   Set tab_number also when there is an error.