SYSLOG: Change configuration selections to assure that one and only one SYSLOG device can be selected.  Also add a check to assure that it is appropriate to use up_putc as the low-level syslog device.  Adds CONFIG_SYSLOG_CONSOLE and CONFIG_SYSLOG_SERIAL_CONSOLE.

SYSLOG: Now a two phase initialization. Some SYSLOG channels cannot be initialized until later in the bringup

-remove a wrong comment in atmel mcan ioctl
-add ioctls to set/get bit timing in stm32l4
-add ioctl hooks to allow future management of can id filters.

assert: Don't define static_assert in C++

Replaces last three commits.  Does the same thing, but does it in a way that does not change the usage model.

Break syslog_channel.c up into syslog_channel.c, syslog_putc.c, syslog_force.c and syslog_flush.c to limited what is brought into the link.  Separate syslog_emergstream.c from syslog_stream.c.  Didn't help in the case I was looking at.

Make system: Build the drivers/ directory even if file descriptors are disabled.  There are still things that may be needed from the drivers/ director (such as SYSLOG logic or lower half drivers).

Remove some last traces of lowvsyslog that were missed; Add a SYSLOG emergency channel for handling assertion output more cleanly

assert: Define static_assert

Remove lowsyslog().  The new syslog() includes all of the functionality of lowsyslog().  No longer any need for two interfaces.

Since syslog_add_intbuffer can now be called from the IDLE thread, it must use a critical section.  Also fix an error in circular buffer index handling.

While working with version 7.10 I discovered a problem in TCP stack that could be observed on high network load. Generally speaking, the problem is that RST flag is set in unnecessary case, in which between loss of some TCP packet and its proper retransmission, another packets had been successfully sent. The scenario is as follows:  NuttX did not receive ACK for some sent packet, so it has been probably lost somewhere. But before its retransmission starts, NuttX is correctly issuing next TCP packets, with sequence numbers increasing properly. When the retransmission of previously lost packet finally succeeds, tcp_input receives the accumulated ACK value, which acknowledges also the packets sent in the meantime (i.e. between unsuccessful sending of lost packet and its proper retransmission). However, variable unackseq is still set to conn->isn + conn->sent, which is truth only if no further packets transmission occurred in the meantime.  Because of incorrect (in such specific case) unackseq value, few lines further condition if (ackseq <= unackseq)is not met, and, as a result, we are going to reset label.