Update configure.ac for autotools 2.71 and fix compile errors from
GCC 11.

	* configure.ac: Replace AC_PROG_LIBTOOL with LT_INIT.

	* Makefile.in: Regenerate.
	* aclocal.m4: Regenerate.
	* configure: Regenerate.
	* src/Makefile.in: regenerate.

	* src/pveclib/vec_int128_ppc.h (vec_sraq): Cast from
	vec_setb_sq() to (vui128_t).
	(vec_sraqi): Cast from vec_setb_sq() to (vui128_t).
	* src/testsuite/vec_int128_dummy.c (test_setb_cyq,
	test_setb_ncq, test_setb_sq): Change type of function result to
	vb128_t.
	* src/testsuite/vec_perf_f64.c (timed_fpclassify_f64):
	Change type of accum to vui64_t.

Signed-off-by: Steven Munroe <munroesj52@gmail.com>