[all] Removed call to getppid in SendPostmasterSignal, replacing with a

[all] Removed call to getppid in SendPostmasterSignal, replacing with a
PostmasterPid variable, which gets set (early) in PostmasterMain
getppid would not be the postmaster?

[fork/exec] Implements processCancelRequest by keeping an array of

pid/cancel_key structs in shared mem

[fork/exec] Moves AttachSharedMemoryAndSemaphores call for backends into
SubPostmasterMain

[win32] Implements reaper/waitpid by keeping an arrays of children
pids,handles in postmaster local mem
      - this item is largely untested, for reasons which should be
obvious, but appears sound

[win32/all] Added extern for pgpipe in Win32 case, and changed the second
pipe call (which seems to have been missed earlier) to pgpipe

[win32] #define'd ftruncate to chsize in the Win32 case

[win32] PG_USLEEP for Win32 has a misplaced paren. Fixed.

[win32] DLLIMPORT handling for MingW case

Claudio Natoli