WND_SCALE: duplicate define check & doc cleanup
bug #49533: start persist timer when unsent seg can't fit in window
Increment ip.drop when dropping due to NULL netif
Add netifapi macros for set link up/down
bug #49684, api_msg: treat non-blocking ERR_MEM as ERR_WOULDBLOCK
Doc: correct minor mis-spelling in sys_arch.txt
bug #49631: handle zero-window probe and refused_data
Task #14314: Add interface name/index APIs