x86: Add evex optimized functions for the wchar_t strcpy family

Implemented:
    wcscat-evex  (+ 905 bytes)
    wcscpy-evex  (+ 674 bytes)
    wcpcpy-evex  (+ 709 bytes)
    wcsncpy-evex (+1358 bytes)
    wcpncpy-evex (+1467 bytes)
    wcsncat-evex (+1213 bytes)

Performance Changes:
    Times are from N = 10 runs of the benchmark suite and are reported
    as geometric mean of all ratios of New Implementation / Best Old
    Implementation. Best Old Implementation was determined with the
    highest ISA implementation.

    wcscat-evex     -> 0.991
    wcscpy-evex     -> 0.587
    wcpcpy-evex     -> 0.695
    wcsncpy-evex    -> 0.719
    wcpncpy-evex    -> 0.694
    wcsncat-evex    -> 0.979

Code Size Changes:
    This change  increase the size of libc.so by ~6.3kb bytes. For
    reference the patch optimizing the normal strcpy family functions
    decreases libc.so by ~5.7kb.

Full check passes on x86-64 and build succeeds for all ISA levels w/
and w/o multiarch.

1 files changed, 31 insertions, 0 deletions

diff --git a/sysdeps/x86_64/wcsncpy-generic.c b/sysdeps/x86_64/wcsncpy-generic.c
new file mode 100644
index 0000000000..0f0ee65b65
--- /dev/null
+++ b/sysdeps/x86_64/wcsncpy-generic.c
@@ -0,0 +1,31 @@
+/* ISA level static dispatch for wcsncpy .c files.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* wcsncpy non-multiarch build is split into two files,
+   wcsncpy-generic.c and wcsncpy.S. The wcsncpy-generic.c build is
+   for ISA level <= 1 and just uses multiarch/wcsncpy-generic.c.
+   This must be split into two files because we cannot include C
+   code from assembly or vice versa.  */
+
+#include <isa-level.h>
+
+#if MINIMUM_X86_ISA_LEVEL <= 3
+
+# include <wcsmbs/wcsncpy.c>
+
+#endif