Made obsolete by now graduated `filetype.lua` (enabled by default).

Note that changes or additions to the filetype detection still need to
be made through a PR to vim/vim as we port the _logic_ as well as tests.

vim-patch:9.0.0771: cannot always tell the difference beween tex and rexx files

Problem:    Cannot always tell the difference beween tex and rexx files.
Solution:   Recognize tex by a leading backslash. (Martin Tournoij,
            closes vim/vim#11380)
https://github.com/vim/vim/commit/bd053f894b0d7652928201faa68c53d1ce2acdc5

Problem:    Filetype of *.sil files not well detected.
Solution:   Inspect the file contents to guess the filetype.
https://github.com/vim/vim/commit/be807d582499acbe314ead3891481cba6ca136df

vim-patch:partial:48c3f4e0bff7

Update runtime files
https://github.com/vim/vim/commit/48c3f4e0bff7efd289a7001b68c777b6f89a7057

partially skip `options.txt` (needs 9.0.0138)

Problem:    Pattern for detecting bitbake files is not sufficient.
Solution:   Adjust the pattern. (Gregory Anders, closes vim/vim#10743)
https://github.com/vim/vim/commit/30e212dac1d29536883c36918a465a38d81d6413

vim-patch:9.0.0055: bitbake files are not detected

Problem:    Bitbake files are not detected.
Solution:   Add bitbake filetype detection by file name and contents. (Gregory
            Anders, closes vim/vim#10697)
https://github.com/vim/vim/commit/fa49eb482729a5fe7da9c9a5ed8d14f68afa55c7

Problem:    Signature files not detected properly.
Solution:   Add a function to better detect signature files. (Doug Kearns)
https://github.com/vim/vim/commit/cdbfc6dbab1d63aa56af316d6b13e37939e7f7a8

Problem:    Not all Visual Basic files are recognized.
Solution:   Change detection of *.cls files. (Doug Kearns)
https://github.com/vim/vim/commit/8b5901e2f9466eb6f38f5b251e871f609f65e252

Update runtime files
https://github.com/vim/vim/commit/75ab590f8504a8912ca0b8c58f6b897bb7a34f07

omit builtin.txt change to `expand()` (depends on 8.2.4726)

Problem:    KRL files using "deffct" not recognized.
Solution:   Adjust the pattern used for matching. (Patrick Meiser-Knosowski,
            closes vim/vim#10200)
https://github.com/vim/vim/commit/93c7a45e86934a92ec513b437fe9b8cc343c53e3