Problem:    Assert_equal() output for dicts is hard to figure out.
Solution:   Only show the different items.
https://github.com/vim/vim/commit/4a021dfbeee88ac09d07e257912485314ecdcabe

This is a port of these two patches combined:

vim-patch:8.1.1524: tests are silently skipped

Problem:    Tests are silently skipped.
Solution:   Throw an exception for skipped tests in more places.
https://github.com/vim/vim/commit/b0f94c1ff34d27d33aa9f96204985ea29c2eb0a1

vim-patch:8.1.1544: some balloon tests don't run when they can

Problem:    Some balloon tests don't run when they can.
Solution:   Split GUI balloon tests off into a separate file. (Ozaki Kiichi,
            closes vim/vim#4538)  Change the feature check into a command for
            consistency.
https://github.com/vim/vim/commit/b46fecd3454399f8ebdc5055302e4bfc5a10f98b

Omit test_lua.vim: previous patches are N/A
Omit test_memory_usage.vim: previous patches are N/A
Omit test_textprop.vim: previous patches are N/A
Omit test_winbar.vim: previous patches are N/A
Omit test_termcodes.vim: mostly N/A
Skip Test_mouse_positon() because it uses test_setmouse().
Cannot throw error in a Test_nocatch_ test.
Use latest `CheckFeature clipboard_working` for test_quotestar.vim

Problem:    More functions can be used as methods.
Solution:   Make a few more functions usable as a method.
https://github.com/vim/vim/commit/e49fbff384e45dd17fed72321c26937edf6de16b

Problem:    Compiling weird regexp pattern is very slow.
Solution:   When reallocating post list increase size by 50%. (Kuang-che Wu,
            closes vim/vim#4012)  Make assert_inrange() accept float values.
https://github.com/vim/vim/commit/38f08e76acf7d21bb34cf8f79f0f82eb63cdc987

Omit changes to typval_compare()
because patch v8.0.1505 was not ported.

Problem:    Assert_equalfile() does not give a hint about the difference.
Solution:   Display the last seen text.
https://github.com/vim/vim/commit/30cc44a97f0ba1349e1a522dab22b11f47888183

Problem:    Assert_equalfile() does not take a third argument.
Solution:   Implement the third argument. (Gary Johnson)
https://github.com/vim/vim/commit/fb517bac2384798bb5142ed1f75f965f93984c0a

Problem:    Assert functions don't return anything.
Solution:   Return non-zero when the assertion fails.
https://github.com/vim/vim/commit/65a5464985f980d2bbbf4e14d39d416dce065ec7

Problem:    Cannot write and read terminal screendumps.
Solution:   Add term_dumpwrite(), term_dumpread() and term_dumpdiff().
            Also add assert_equalfile().
https://github.com/vim/vim/commit/d96ff165113ce5fe62107add590997660e3d4802

Problem:    Assert_fails() does not fail inside try/catch.
Solution:   Set trylevel to zero. (Ozaki Kiichi, closes vim/vim#4639)
https://github.com/vim/vim/commit/7780e5c1c5485a979ab6e3914a43e17912e213a8