Integrate LWIP critical section changes

[earlephilhower]

Just a friendly reminder to @d-a-v so the LWIP fixes he's done get pulled into the main repo. I've gone through and updated the other 3 submodules, and think that (and UMM) are the only ones left...

[d-a-v]

Once UMM is merged, I'll make an update for both lwip1 and lwip2

[devyte]

umm changes were merged with #6274.