* fork-child.c (fork_inferior): Set inferior_pid before calling
init_trace_fun. Move the code which gets us through the shell
to new function startup_inferior.
* inferior.h: Declare startup_inferior.
* procfs.c (procfs_init_inferior), inftarg.c (ptrace_him):
Call startup_inferior.
* m3-nat.c (m3_trace_him): Call intercept_exec_calls.
* config/nm-m3.h: Don't define STARTUP_INFERIOR.
* config/i386/tm-i386m3.h, config/ns32k/tm-ns32k.h,
config/mips/tm-mipsm3.h: Don't define START_INFERIOR_TRAPS_EXPECTED.