Ptrace sane block

Built on top of !128 (merged). Depends on syscall!47 (merged). It diverges ptrace behavior from the RFC, to work in an arguably saner way.

Before, the write call would sleep (in blocking mode) until it was read. Now the read call does that instead. This gets rid of the PTRACE_WAIT flag, whose job was partially to allow waiting without also doing the other things that write usually does (setting breakpoints and stuff)