Change borrow debugging so it is disabled by -O
Correct mismatch between the way that pattern ids and expression ids map to types (pattern ids map to the input type, expression ids map to the output type)
lang: um, actually set locking bits! this code got lost.
rustc: add rooting, write-guards to slices etc
factor code for write guards into its own module; add neglected resolve_stage0
improve DEBUG_BORROW printouts
make asm_comments something that you opt in to
separate out write_guard code into its own module
disable lang debug for perf
add warning for #6248 and remove instances of it
Address all FIXMEs from #5562