* procfs.c: Cleanup of procfs tracing. Move defines and
prototypes to proc-utils.h
* proc-utils.h: Define tracing macros. Declare trace functions.
* proc-api.c: Make procfs tracing a runtime option.
(prepare_to_trace): New function, abstracted out of several
places. Open a trace file if one is required.
(ioctl_with_trace, write_with_trace, open_with_trace,
close_with_trace, wait_with_trace, lseek_with_trace):
Report errno if an error occurs in a system call.
(write_with_trace): Make 2nd arg void *, to agree with write.
