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

goalc/compiler/compilation/Atoms.cpp

@@ -58,6 +58,11 @@ static const std::unordered_map<
         {":cont", &Compiler::compile_cont},
         {":break", &Compiler::compile_break},
         {":dump-all-mem", &Compiler::compile_dump_all},
+        {":pm", &Compiler::compile_pm},
+        {":di", &Compiler::compile_di},
+        {":disasm", &Compiler::compile_disasm},
+        {":bp", &Compiler::compile_bp},
+        {":ubp", &Compiler::compile_ubp},
 
         // TYPE
         {"deftype", &Compiler::compile_deftype},