Add the necessary infrastructure to handle restartable syscalls via
the restart_block method.  This isn't perfect, since we are unable
to modify the syscall number with ARM executables (it's typically
encoded into the instruction in the text segment) so instead we
build some code on the user space stack.

There is a potential problem - what happens if we are sleeping,
someone suspends us, resume (we continue to sleep via the restart
block method) suspend and then resume again?  We will build two
sets of restart code on the user stack.  This is probably a little
inefficient, but it should be harmless.