6loWPAN:  Add some checks for the case where there are multiple network devices and multiple link layer protocols.

not a clean fix, but at least makes DHCP working with CONFIG_NETDEV_MULTINIC

Approved-by: Gregory Nutt <gnutt@nuttx.org>

Revert "Add a placeholder for nucleo-64 boards.  Currently these are in various directories nucleo-f303re, nucleo-f334r8, and nucleo-l476rg but need to be consolidated here because these are all the same boards."

This reverts commit 935cc4e3.

Add a placeholder for nucleo-64 boards.  Currently these are in various directories nucleo-f303re, nucleo-f334r8, and nucleo-l476rg but need to be consolidated here because these are all the same boards.

sched: Fix tg_flags check with GROUP_FLAG_NOCLDWAIT

Approved-by: Gregory Nutt <gnutt@nuttx.org>

Jira: PDFW15IS-208
Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

Adds USB host support to stm32f411-disco board.

Approved-by: Gregory Nutt <gnutt@nuttx.org>

TUN driver: Implement TAP (OSI layer 2) mode.

Approved-by: Gregory Nutt <gnutt@nuttx.org>

Enable by setting the IFF_TAP flag instead of the IFF_TUN flag in ifr_flags.

libc/netdb: in dns_query_callback, ret != -EADDRNOTAVAIL condition consumes error returns including EAGAIN in this case, dns query retransmission doesn't work

Add logic to disable cancellation points within the OS.  This is useful when an internal OS function that is NOT a cancellation point calls an OS function which is a cancellation point.  In that case, irrecoverable states may occur if the cancellation is within the OS.

STM32F7: serial: disallow broken configuration combination of CONFIG_STM32F7_FLOWCONTROL_BROKEN=y and CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS not set.