Fixes instigated by attempting to compile Tcl-7.6.
- gettimeofday() used wrong device for time sampling
- vfprintf.c ignored left justification in favour of zero left padding
- wait.c was rewritten to reap processes by PID
- _buf.c miscalculated the number of open FDs in select()
- added wait3() and wait4() prototypes to "sys/wait.h"
- unprotected hypot() prototype in "math.h".