Add GEN_START support (#392)

* Apparently should be enough ?

* Add `GEN_START` test

* Add `GEN_START` test compiled

* Add `GEN_START` test tokenized

* Smaller test since only POP is needed.

* Smaller test since only POP is needed.

* Smaller test since only POP is needed.

* dos2unix

ASTree.cpp

@@ -2419,6 +2419,9 @@ PycRef<ASTNode> BuildFromCode(PycRef<PycCode> code, PycModule* mod)
         case Pyc::PUSH_NULL:
             stack.push(nullptr);
             break;
+        case Pyc::GEN_START_A:
+            stack.pop();
+            break;
         default:
             fprintf(stderr, "Unsupported opcode: %s\n", Pyc::OpcodeName(opcode & 0xFF));
             cleanBuild = false;