Doc: Move builtin documentation to a new chapter [PR42270]

This is part of an incremental effort to make the documentation for
GCC extensions better organized by grouping/rearranging sections by
topic.

I was originally intending to consolidate all the sections documenting
builtins as subsections of a new container section within the C
extensions chapter, but I ran into a technical limitation of Texinfo:
it only supports sectioning depth up to @subsubsection, and we already
had quite a few of those in the target-specific builtins sections.  So
instead I have pulled all the existing sections out into a new
chapter.  This actually makes sense since some of the builtins are
specific to C++ anyway and are not C language extensions at all.

Subsequent patches in this series will move things around within the
new chapter; this one just adds the new container node and adjusts
the menus.

gcc/ChangeLog
	PR other/42270
	* doc/extend.texi (C Extensions): Move menu items for
	builtin-related sections to...
	(Built-in Functions): New chapter.
	* doc/gcc.texi (Introduction): Add menu entry for new chapter.

0 files changed, 0 insertions, 0 deletions