This commit moves all of the libraries under a common directory called libs/. This most certainly break libcxx and uClibc++ for now.

Squashed commit of the following:

    libs/libxx:  Fix some confusing in naming.  If the directory is called libxx, then the library must be libxx.a (unless perhaps LIBCXX is selected).
    libs/:  Fix paths in moved library directories.
    libs:  Brute force move of libc, libnx, and libxx to libs.  Cannot yet build it in that configuration.

libs/libc/aio/aio_error.c

@@ -0,0 +1,114 @@
+/****************************************************************************
+ * libs/libc/aio/aio_error.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <aio.h>
+#include <assert.h>
+#include <errno.h>
+
+#ifdef CONFIG_FS_AIO
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* Configuration ************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: aio_error
+ *
+ * Description:
+ *   The aio_error() function returns the error status associated with the
+ *   aiocb structure referenced by the aiocbp argument. The error status fo
+ *   an asynchronous I/O operation is the errno value that would be set by
+ *   the corresponding read(), write(), fdatasync(), or fsync() operation. If
+ *   the operation has not yet completed, then the error status will be equal
+ *   to EINPROGRESS.
+ *
+ * Input Parameters:
+ *   aiocbp - A pointer to an instance of struct aiocb
+ *
+ * Returned Value:
+ *   If the asynchronous I/O operation has completed successfully, then 0
+ *   will be returned. If the asynchronous operation has completed
+ *   unsuccessfully, then the error status, as described for read(),
+ *   write(), fdatasync(), and fsync(), will be returned. If the
+ *   asynchronous I/O operation has not yet completed, then EINPROGRESS will
+ *   be returned.
+ *
+ *   The aio_error() function may fail if:
+ *
+ *     EINVAL - The aiocbp argument does not refer to an asynchronous
+ *       operation whose return status has not yet been retrieved.
+ *
+ ****************************************************************************/
+
+int aio_error(FAR const struct aiocb *aiocbp)
+{
+  DEBUGASSERT(aiocbp);
+
+  if (aiocbp->aio_result < 0)
+    {
+      return -aiocbp->aio_result;
+    }
+
+  return OK;
+}
+
+#endif /* CONFIG_FS_AIO */