runtime(cpp): Fix digit separator in syntax script for octals and floats

Also fix the incorrect rendering of floats that start with ".".

closes: vim/vim#14724

https://github.com/vim/vim/commit/c5def6561d5612487ac3523787da1c26335b17e1

Co-authored-by: Wu Yongwei <wuyongwei@gmail.com>

runtime(syntax): unlet b:filetype_in_cpp_family for cpp & squirrel

Update runtime/syntax/cpp.vim and runtime/syntax/squirrel.vim to unlet
b:filetype_in_cpp_family as it remains set even after updating the ft of
a file manually or through a modeline, not allowing c specific keywords
to be highlighted.

Since the variable b:filetype_in_cpp_family is only used by the c.vim
syntax script, unlet it directly after sourcing the c.vim runtime file
instead of at the end of the script.

Also update the last Change Header for both files.

closes: vim/vim#13650

https://github.com/vim/vim/commit/ff0baca86523f1e8c6ea593ec0ef2f9860f001d0

Co-authored-by: laburnumT <laburnumtec@gmail.com>

Update runtime files
https://github.com/vim/vim/commit/89a9c159f23fb7b3e24e6d09068adfc24a73afcb

Omit:
nsis/lang/turkish.nsi
pixmaps/gen-inline-pixbufs.sh
doc/popup.txt
doc/terminal.txt
tutor/tutor*
src/[g]vimtutor
CONTRIBUTING.md

Skip:
doc/eval.txt (needs 8.1.2342)
doc/testing.txt (needs 8.2.0299)

Update runtime files
https://github.com/vim/vim/commit/d2ea7cf10a4d026ebd402594d656af7d5c811c24

omit `runtime/doc/if_tcl.txt`
omit `runtime/doc/textprop.txt`
omit `runtime/tutor/*`
omit `runtime/syntax/vim.vim` (cherry-picked in https://github.com/neovim/neovim/commit/2dd7828511d04a8b7f1ac4331c719a751a5db869)

manual merge of `runtime/pack/dist/opt/termdebug/plugin/termdebug.vim`

Update runtime files.
https://github.com/vim/vim/commit/98a29d00a48e15a50e2850e1a29b7d475c531b0c

Update runtime files.
https://github.com/vim/vim/commit/95a9dd1efc5ae3221865f4970053a5708557e682

Update runtime files.

https://github.com/vim/vim/commit/6aa8cea46d4179b2617daae034063dd0d8054e35

Runtime file updates.

https://github.com/vim/vim/commit/b4ada79aa7d0d1e5da3a659b1a203d7cae9f7f59

Closes #5055

Updated runtime files.  Remove HiLink commands.

https://github.com/vim/vim/commit/f37506f60f87d52a9e8850e30067645e2b13783c

Updated runtime files.  Remove version checks for Vim older than 6.0.

https://github.com/vim/vim/commit/89bcfda6834aba724d12554a34b9ed49f5789fd5