* sigproc.cc (proc_info): Rename proc_exists which takes a pid to "pid_exists".

* shared.h: Split out "child_info" stuff into a new header file and use where
necessary.  Declare pid_exists.
* child_info.h: New file.

winsup/cygwin/spawn.cc

@@ -26,6 +26,7 @@ details. */
 #include "dtable.h"
 #include "sync.h"
 #include "sigproc.h"
+#include "child_info.h"
 #include "pinfo.h"
 #include "perthread.h"