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/netdb/lib_gethostbyaddr.c

@@ -0,0 +1,92 @@
+/****************************************************************************
+ * libs/libc/netdb/lib_gethostbyaddr.c
+ *
+ *   Copyright (C) 2015 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 <netdb.h>
+#include <errno.h>
+
+#include "libc.h"
+#include "netdb/lib_netdb.h"
+
+#ifdef CONFIG_NETDB_HOSTFILE
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: gethostbyaddr
+ *
+ * Description:
+ *   The gethostbyaddr() function returns a structure of type hostent for
+ *   the given host address addr of length len and address type type. Valid
+ *   address types are AF_INET and AF_INET6. The host address argument is a
+ *   pointer to a struct of a type depending on the address type, for example
+ *   a struct in_addr *  for address type AF_INET.
+ *
+ * Input Parameters:
+ *   addr - The address of the host to find.
+ *   len - The length of the address
+ *   type - The type of the address
+ *
+ * Returned Value:
+ *   Upon successful completion, this function will return a pointer to a
+ *   hostent structure if the requested entry was found, and a null pointer
+ *   if the end of the database was reached or the requested entry was not
+ *   found.
+ *
+ *   Upon unsuccessful completion, gethostbyaddr() will set h_errno to
+ *   indicate the error
+ *
+ ****************************************************************************/
+
+FAR struct hostent *gethostbyaddr(FAR const void *addr, socklen_t len, int type)
+{
+  int ret;
+
+  DEBUGASSERT(addr != NULL);
+  DEBUGASSERT(type == AF_INET || type == AF_INET6);
+
+  ret = gethostbyaddr_r(addr, len, type, &g_hostent, g_hostbuffer,
+                        CONFIG_NETDB_BUFSIZE, &h_errno);
+  return ret == 0 ? &g_hostent : NULL;
+}
+
+#endif /* CONFIG_NETDB_HOSTFILE */