busybox

lineedit: stop using both data/bss and tons of stack.
stack usage was ~10 kb!
unfortunately, noticeable code size growth:
   text    data     bss     dec     hex filename
   9252      12     181    9445    24e5 busybox.t7/libbb/lineedit.o
   9714       4       0    9718    25f6 busybox.t8/libbb/lineedit.o