[libc] Update errno and strto* files for compatibility

Most of the strto* functions are only stubbed out, but they're there for
things that link to them but don't call them.

src/libraries/libc/wchar/wcstof.cpp

@@ -0,0 +1,18 @@
+/** \file wcstof.cpp
+  *
+  * This file is part of the C standard library for the jsix operating
+  * system.
+  *
+  * This Source Code Form is subject to the terms of the Mozilla Public
+  * License, v. 2.0. If a copy of the MPL was not distributed with this
+  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+  */
+
+#include <assert.h>
+#include <wchar.h>
+
+float wcstof(const wchar_t * restrict nptr, wchar_t ** restrict endptr)
+{
+    assert(!"wcstof() NYI");
+    return 0;
+}