rs6000: Support for vectorizing built-in functions

This patch just duplicates a couple of functions and adjusts them to use the
new builtin names.  There's no logical change otherwise.

2021-09-17  Bill Schmidt  <wschmidt@linux.ibm.com>

gcc/
	* config/rs6000/rs6000.c (rs6000-builtins.h): New include.
	(rs6000_new_builtin_vectorized_function): New function.
	(rs6000_new_builtin_md_vectorized_function): Likewise.
	(rs6000_builtin_vectorized_function): Call
	rs6000_new_builtin_vectorized_function.
	(rs6000_builtin_md_vectorized_function): Call
	rs6000_new_builtin_md_vectorized_function.