Squashed commit of the following:
sched/sched/sched_getsockets.c: Fix an error in conditional compilation.
fs/: Remove all conditional logic based on CONFIG_NSOCKET_DESCRIPTORS == 0
Documentation/: Remove all references to CONFIG_NSOCKET_DESCRIPTORS == 0
include/: Remove all conditional logic based on CONFIG_NSOCKET_DESCRIPTORS == 0
libs/: Remove all conditional logic based on CONFIG_NSOCKET_DESCRIPTORS == 0
net/: Remove all conditional logic based on CONFIG_NSOCKET_DESCRIPTORS == 0
sched/: Remove all conditional logic based on CONFIG_NSOCKET_DESCRIPTORS == 0
syscall/: Remove all conditional logic based on CONFIG_NSOCKET_DESCRIPTORS == 0
tools/: Fixups for CONFIG_NSOCKET_DESCRIPTORS no longer used to disable sockets.
net/tcp: Add logic to send probes when SO_KEEPALIVE is enabled.
net/tcp: TCP socket should not have to be connected to configure KeepAlive.
net/: Add a separate configuration to enable/disable KEEPALIVE socket options.
net/tcp: Arguments to TCP keep-alive timing functions probably should be struct timeval as are the times for other time-related socket options.
net/tcp: Fix a backward conditional
net/tcp: Add some more checks and debug output to TCP-protocol socket options.
net/tcp: Cosmetic changes to some alignment.
net/: Adds socket options needed to manage TCP-keepalive and TCP state machine logic to detect if that the remote peer is alive. Still missing the timer poll logic to send the keep-alive probes and the state machine logic to respond to probes.
