Add the 'unix-system-call' macro

extra/unix/system-call/system-call.factor

@@ -0,0 +1,15 @@
+
+USING: kernel continuations sequences math accessors inference macros
+       fry arrays.lib unix ;
+
+IN: unix.system-call
+
+ERROR: unix-system-call-error word args message ;
+
+MACRO: unix-system-call ( quot -- )
+  [ ] [ infer in>> ] [ first ] tri
+ '[
+    [ @ dup 0 < [ dup throw ] [ ] if ]
+    [ drop , narray , swap err_no strerror unix-system-call-error ]
+    recover
+  ] ;