ENH: check in almost building VMS stuff with VMSBuild directory since the bootstrap script will not work on VMS

COMP:Fixed gcc 4.3.2 warning with -O1 and above: ignoring return value of read'), declared with attribute warn_unused_result

According to "man select" on Linux it is possible that select() lies
about data being ready on a pipe in some subtle cases.  We deal with
this by switching to non-blocking i/o and checking for EAGAIN.  See
issue #7180.

ENH: all ctype function have the same issue: char can be signed or unsigned, since isspace only deal with >=0 value (except EOF) one has to first cast it to unsigned char

BUG: Fix hang in Process_Kill on OS X caused by an OS bug in which a pipe read end cannot be closed if the pipe write end is open, the pipe is full, and another process is blocking waiting to write.  Work around the problem by killing the children before closing the pipes.

BUG: Do not send both SIGSTOP and SIGKILL when killing a process.  The SIGSTOP seems to be able to block the SIGKILL occasionally.  Also the SIGKILL is sufficient since the process table entry will still exist until it is reaped with waitpid.

ENH: Changes based on patch from Ryan C. Gordon to enable process execution on BeOS.  There seems to be no way to implement it without polling (or threads).

ENH: Adding tests KWSYS_C_HAS_PTRDIFF_T and KWSYS_C_HAS_SSIZE_T to help ProcessUNIX.c build everywhere without warnings.

ENH: Added Process_SetPipeNative method to allow user code to override the pipes connected to the child pipeline.

COMP: Use SA_RESTART only if it is defined for the current platform.  This partially addresses bug#3556.

ENH: Implemented handling of SIGCHLD to detect the termination of immediate children.  This allows grandchildren to remain running after the children exit.

BUG: When more than one command is given and one of them fails to start and the rest are killed, do not forget to reap the killed children.

BUG: struct timeval uses unsigned types on at least one platform (QNX).  Alot of the time logic assumes a signed type.  Switch to using a signed representation that is converted to the native representation only for system calls.