Add some debugger memory utilities (#109)

* add some memory utilities

* run waitpid in a separate thread and support very simple breakpoints

* fix breakpoints

* add missing windows stub function

* fix error message on exit

goal_src/goal-lib.gc

@@ -102,6 +102,37 @@
     )
   )
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; DEBUGGER MACROS
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defmacro db (&rest args)
+  `(:pm 1 ,@args)
+  )
+
+(defmacro dh (&rest args)
+  `(:pm 2 ,@args)
+  )
+
+(defmacro dw (&rest args)
+  `(:pm 4 ,@args)
+  )
+
+(defmacro dd (&rest args)
+  `(:pm 8 ,@args)
+  )
+
+(defmacro df (&rest args)
+  `(:pm 4 ,@args :print-mode float)
+  )
+
+(defmacro segfault ()
+  `(-> (the (pointer int) 0))
+  )
+
+(defmacro fpe ()
+  `(/ 0 0)
+  )
 
 ;;;;;;;;;;;;;;;;;;;
 ;; GOAL Syntax