Cygwin: pinfo: Fix exit code for non-cygwin apps which reads console.

Cygwin: pinfo: Fix exit code for non-cygwin apps which reads console.

- The recent commit "Cygwin: pinfo: Fix exit code when non-cygwin app
  exits by Ctrl-C." did not fix enough the issue. If a non-cygwin app
  is reading the console, it will not return STATUS_CONTROL_C_EXIT
  even if it is terminated by Ctrl-C. As a result, the previous patch
  does not take effect.
  This patch solves this issue by setting sigExeced to SIGINT in
  ctrl_c_handler(). In addition, sigExeced will be cleared if the app
  does not terminated within predetermined time period. The reason is
  that the app does not seem to be terminated by the signal sigExeced.