Avoid overwrite of local variables when using
short (int, etc.) types with XtVaGetValues().
Cast XtPointer using (XtArgVal) without
the need to use C99 <stdint.h> and friends.
Patch from Pascal Stumpf <Pascal.Stumpf@cubes.de>
The official POSIX name for this signal is SIGCHLD. Linux probably
has SIGCLD only for SysV compatibility, but BSD does not.