Problem:  Strange error when heredoc marker starts with "trim".
Solution: Check for whitespace after "trim" or "eval" (zeertzjq)

For :python3 etc., a heredoc marker that starts with a lower-case letter
is valid, and when it starts with "trim" it works in a script but not in
a function, and this PR makes it works in a function.
For :let, a heredoc marker that starts with a lower-case letter is not
valid, but when it starts with "trim" or "eval" the error can be a bit
confusing in a function, and this PR make it less confusing.

closes: vim/vim#16574

https://github.com/vim/vim/commit/449c2e5454735fe1cfc8c21b2c6880d6bdf4cd6e

Problem:    "clear" macros are not always used.
Solution:   Use ALLOC_ONE, VIM_CLEAR, CLEAR_POINTER and CLEAR_FIELD in more
            places. (Yegappan Lakshmanan, closes vim/vim#12104)

https://github.com/vim/vim/commit/960dcbd098c761dd623bec9492d5391ff6e8dceb

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

Problem:    Cannot use Perl heredoc in nested :def function. (Virginia
            Senioria)
Solution:   Only concatenate heredoc lines when not in a nested function.
            (closes vim/vim#10415)

https://github.com/vim/vim/commit/d881d1598467d88808bafd2fa86982ebbca7dcc1

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Problem:  Arguments of a function are missing after failing to redefine
          it (after 8.2.2505), and heap-use-after-free with script-local
          function (after 9.1.1063).
Solution: Don't clear arguments or free uf_name_exp when failing to
          redefine an existing function (zeertzjq)

closes: vim/vim#16567

https://github.com/vim/vim/commit/04d2a3fdc051d6a419dc0ea4de7a9640cefccd31

Problem:  heap-use-after-free and stack-use-after-scope with :14verbose
          when using :return and :try (after 9.1.1063).
Solution: Move back the vim_free(tofree) and the scope of numbuf[].
          (zeertzjq)

closes: vim/vim#16563

https://github.com/vim/vim/commit/2101230f4013860dbafcb0cab3f4e6bc92fb6f35

Problem:  too many strlen() calls in userfunc.c
Solution: refactor userfunc.c and remove calls to strlen(),
          drop set_ufunc_name() and roll it into alloc_ufunc(),
          check for out-of-memory condition in trans_function_name_ext()
          (John Marriott)

closes: vim/vim#16537

https://github.com/vim/vim/commit/b32800f7c51c866dc0e87244eb4902540982309d

Add missing change to call_user_func() from patch 8.1.1007.
Consistently use PRIdSCID instead of PRId64 for script IDs.

Co-authored-by: John Marriott <basilisk@internode.on.net>

Problem:    Crash and/or memory leak when redefining function after error.
Solution:   Clear pointer after making a copy.  Clear arrays on failure.
            (closes vim/vim#11774)

https://github.com/vim/vim/commit/f057171d8b562c72334fd7c15c89ff787358ce3a

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Problem:    Vim9: crash after defining function with invalid return type.
Solution:   Clear function growarrays.  Fix memory leak.

https://github.com/vim/vim/commit/31842cd0772b557eb9584a13740430db29de8a51

Cherry-pick free_fp from patch 8.2.3812.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Problem:    Vim9: function expanded name is cleared when sourcing a script
            again.
Solution:   Only clear the expanded name when deleting the function.
            (closes vim/vim#6707)

https://github.com/vim/vim/commit/c4ce36d48698669f81ec90f7c9dc9ab8c362e538

Co-authored-by: Bram Moolenaar <Bram@vim.org>