Instead of declaring an enum, this creates a global variable. As gcc10
uses -fno-common by default, global variables declared with the same
name more than once is not allowed anymore revealing this issue.

Each time this header is included, we define the enum name as a global
variable.

See also https://bugzilla.redhat.com/show_bug.cgi?id=1799680

Problem:    Reloading a script gives errors for existing functions.
Solution:   Allow redefining a function once when reloading a script.
https://github.com/vim/vim/commit/ded5f1bed7ff2d138b3ee0f9610d17290b62692d

Problem:    Cannot get the script line number when executing a function.
Solution:   Store the line number besides the script ID. (Ozaki Kiichi,
            closes vim/vim#3362)  Also display the line number with ":verbose set".
https://github.com/vim/vim/commit/f29c1c6aa3f365c025890fab5fb9efbe88eb1761

- Re-enable Test_BufLeave_Wipe. 66f5e5c7d7ce

This is my (probably-wrong) application of Zyx's suggestion in #9163:

> free_buffer_stuff() already removes changedtick. It is better to
> make `free_options` a flag variable and avoid calling
> buf_init_changedtick() based on some flag there: current workflow
> looks weird as it first removes `b:changedtick`, then re-adds it
> by calling buf_init_changedtick(), then remove again.

> Also based on my understanding it looks logical to not remove
> `b:changedtick`, but to *replace* it with something allocated if
> needed based on examining reference count before calling
> `unref_var_dict`. Because now you have key disappearing from
> dictionary for no good reason.

Patch-By: Nikolai Aleksandrovich Pavlov <kp-pav@yandex.ru>

Problem:    Floating point exception with "%= 0" and "/= 0".
Solution:   Avoid dividing by zero. (Dominique Pelle, closes vim/vim#4058)
https://github.com/vim/vim/commit/e21c1580b7acb598a6e3c38565434fe5d0e2ad7a

Despite the PVS warning, we do not want to conflate these
cases, they are semantically different.

Problem:    Lock flag in new dictitem is reset in many places.
Solution:   Always reset the lock flag.
https://github.com/vim/vim/commit/c89d4b35300b98cf68b14c89c8e1add51bd857e3

Problem:    ":profdel func" does not work if func was called already.
            (Dominique Pelle)
Solution:   Reset uf_profiling and add a flag to indicate initialization was
            done.
https://github.com/vim/vim/commit/ad6480961080f80a455b2394f27b02935a2ded52

Problem:    Incomplete set of assignment operators.
Solution:   Add /=, *= and %=. (Ozaki Kiichi, closes vim/vim#3931)
https://github.com/vim/vim/commit/ff697e6cef8ced7717a21fd525ab3200b2f1724f