apparently some other archs have sys/io.h and should not break just
because they don't have the x86 port io functions. provide a blank
bits/io.h everywhere for now.
incomplete but at least partly working. requires all files to be
compiled in the new "secure" plt model, not the old one that put plt
code in the data segment. TLS is untested but may work. invoking the
dynamic linker explicitly to load a program does not yet handle argv
correctly.