v2: DOCUMENTATION_ROOT_URL vs. release branches [PR114738]

This patch moves the documentation root URL infix for release branches
from get_option_url/make_doc_url to configure, such that only the default
changes and when users specify a custom documentation root URL, they don't
have to add gcc-MAJOR.MINOR.0 subdirectories for release branches.

Tested by checking
../configure --disable-bootstrap --enable-languages=c --disable-multilib
built trunk on
void
foo (int x)
{
  __builtin_printf ("%ld\n", x);
}
testcase and looking for the URL in there, then repeating that after
changing gcc/BASE-VER to 14.1.0 and again after changing it to 14.1.1,
plus normal bootstrap/regtest.

2024-04-24  Jakub Jelinek  <jakub@redhat.com>

	PR other/114738
	* opts.cc (get_option_url): Revert 2024-04-17 changes.
	* gcc-urlifier.cc: Don't include diagnostic-core.h.
	(gcc_urlifier::make_doc_url): Revert 2024-04-17 changes.
	* configure.ac (documentation-root-url): On release branches
	append gcc-MAJOR.MINOR.0/ to the default DOCUMENTATION_ROOT_URL.
	* doc/install.texi (--with-documentation-root-url=): Document
	the change of the default.
	* configure: Regenerate.