Fix binutils build on hppa64-hpux with gcc-16 (v3)

With recent gcc versions, implicit function declarations are errors.
We need to ensure that ffs() and strtoull() are declared and correctly
checked for by configure.

strtoull() is not declared on hpux but it's provided by libiberty.

An unnecessary include of strings.h in elf32-xtensa.c is removed.

Approved-By: Jan Beulich <jbeulich@suse.com>

2025-12-14  John David Anglin  <danglin@gcc.gnu.org>

bfd/ChangeLog:

	* configure.ac: Check for strtoull declaration.
	* elf32-xtensa.c: Remove strings.h include.
	* configure: Regenerate.
	* config.in: Regenerate.
	* sysdep.h: Include strings.h and declare strtoull()
	if a declaration for it isn't found by configure.

ld/ChangeLog:

	* configure.ac: Check for strtoull declaration.
	* configure: Regenerate.
	* config.in: Regenerate.
	* sysdep.h: Declare strtoull() if a declaration for it
	isn't found by configure.