also remove binary on make clean
use static functions to not encapsulate proc->in_syscall
kill dead code

Ok, that's not exactly dead code but comments about the syscall to
handle, but that's not much more useful. We'll add the syscall that we
need when we encounter them.
reindent, no real change
allow to compare straces on msg test
merge syscall_sendmsg_{pre,post} into a single handler doing both
merge syscall_write_{pre,post} into a single handler doing both
merge syscall_read_{pre,post} into a single handler doing both
merge syscall_open_post and its caller into a single handler doing both