kernel: move kernel code to kernel/ directly

Also remove mentions of unified kernel in various places in the kernel,
samples and documentation.

Change-Id: Ice43bc73badbe7e14bae40fd6f2a302f6528a77d
Signed-off-by: Anas Nashif <anas.nashif@intel.com>

kernel/errno.c

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2015 Wind River Systems, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/** @file
+ *
+ * @brief Per-thread errno accessor function
+ *
+ * Allow accessing the errno for the current thread without involving the
+ * context switching.
+ */
+
+#include <kernel_structs.h>
+
+/*
+ * Define _k_neg_eagain for use in assembly files as errno.h is
+ * not assembly language safe.
+ * FIXME: wastes 4 bytes
+ */
+const int _k_neg_eagain = -EAGAIN;
+
+#ifdef CONFIG_ERRNO
+int *_get_errno(void)
+{
+	return &_current->errno_var;
+}
+#endif