[php-src] Issue #24489: master: part of the mbstring bailout fix got lost in a merge

Issue: https://github.com/php/php-src/issues/24489 Author: dev-null-undefined The PHP-8.6 into master merge 9705fda1bb dropped this hunk from mb_convert_buf_ensure() in ext/mbstring/libmbfl/mbfl/mbfl_encoding.h. It also dropped the test ext/mbstring/tests/oom_buf_growth.phpt: ```diff if (!newstr) { + /* An earlier growth may have moved the buffer. */ + buf->out = *out; + buf->limit = *limit; return FAILURE; } ``` Both are on PHP-8.6 but missing on master. git diff origin/master origin/PHP-8.6 -- ext/mbstring/libmbfl/mbfl/mbfl_encoding.h shows only this hunk, and git show --remerge-diff 9705fda1bb -- ext/mbstring shows the merge removing it. I'm guessing it was an accident during conflict resolution. Re-applying the three lines and restoring the test from PHP-8.6 should be all that's needed.