KWSys SystemInformation: No SA_RESTART on QNX

QNX not support SA_RESTART signal:

 /* #define SA_RESTART 0x0040 (not supported yet) */

Use it in SystemInformation only if it is defined.
Merge topic 'backport-kwsys-qnx-fix'

cc3248f4 KWSys SystemInformation: No SA_RESTART on QNX