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/stdio/lib_fseek.c

@@ -0,0 +1,102 @@
+/****************************************************************************
+ * libs/libc/stdio/lib_fseek.c
+ *
+ *   Copyright (C) 2007, 2008, 2011, 2013, 2017 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 <sys/types.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include "libc.h"
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: fseek
+ *
+ * Description:
+ *   The fseek() function sets the file position indicator for the stream
+ *   pointed to by stream. The new position, measured in bytes, is obtained
+ *   by adding offset bytes to the position specified by whence. If whence is
+ *   set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to the
+ *   start of the file, the current position indicator, or end-of-file,
+ *   respectively. A successful call to the fseek() function clears the
+ *   end-of-file indicator for the stream and undoes any effects of the ungetc(3)
+ *   function on the same stream.
+ *
+ * Returned Value:
+ *   Zero on succes; -1 on failure with errno set appropriately.
+ *
+ ****************************************************************************/
+
+int fseek(FAR FILE *stream, long int offset, int whence)
+{
+#ifdef CONFIG_DEBUG_FEATURES
+  /* Verify that we were provided with a stream */
+
+  if (!stream)
+    {
+      set_errno(EBADF);
+      return ERROR;
+    }
+#endif
+
+#ifndef CONFIG_STDIO_DISABLE_BUFFERING
+  /* Flush any valid read/write data in the buffer (also verifies stream) */
+
+  if (lib_rdflush(stream) < 0 || lib_wrflush(stream) < 0)
+    {
+      return ERROR;
+    }
+#endif
+
+  /* On success or failure, discard any characters saved by ungetc() */
+
+#if CONFIG_NUNGET_CHARS > 0
+  stream->fs_nungotten = 0;
+#endif
+
+  /* Perform the fseek on the underlying file descriptor */
+
+  return lseek(stream->fs_fd, offset, whence) == (off_t)-1 ? ERROR : OK;
+}