Merge pull request #14 from sunfishcode/incoming

Instead of lowering pointers, teach the JSBackend how to handle them
fix ashr when high bits are exactly 0
typo fix
emit an abort if calling an absolute address
emit nothing for lifetime intrinsics
only emit declares with uses
support reserved function pointers
leave lines with calls to no-ops without a ;
guarantee that sanitize() returns a proper non-colliding value for each input
version 1.11.1
Minor code simplifications.