Merge from origin/emacs-28

3e4eb54 ; * etc/PROBLEMS: Minor copyedits of the last change.  (Bug#5...
35bc211 Document a macOS error message when opening Emacs
4df9998 Fix header-line and tab-line when mode-line-compact is set
81915a9 Add manual section about how to avoid regexp problems
a16e66c Clarify build environment
6ab6b2f Clarify build directory structure
9d61620 * src/pdumper.c (dump_do_dump_relocation): Add sanity check.

diff --cc doc/lispref/searching.texi
Simple merge

diff --cc etc/PROBLEMS
Simple merge

diff --cc src/pdumper.c
Simple merge

diff --cc src/xdisp.c
Simple merge