Fixed a 'malformed assignment' issue, read more

I've also added some support for compiler errors in general, but these
will get expanded on later.

I've also quickly added a valgrind option to the tests and found a few
leaks. I'll deal with these later.

Summary of changes:

* Clarified the lifetime of the bytecode in memory
* Erroneous routines exit without compiling
* Empty VMs don't run
* Added a check for malformed assignments
* Renamed "routine" to "module" within the VM
* VM no longer tries to free the bytecode - must be done manually
* Started experimenting with valgrind, not yet ready

makefile

@@ -50,6 +50,18 @@ test-cases-gdb:
 test-integrations-gdb:
 	$(MAKE) -C $(TOY_INTEGRATIONSDIR) gdb -k
 
+#same as above, but with valgrind
+.PHONY: tests-valgrind
+tests-valgrind: clean test-cases-valgrind test-integrations-valgrind
+
+.PHONY: test-cases-valgrind
+test-cases-valgrind:
+	$(MAKE) -C $(TOY_CASESDIR) valgrind -k
+
+.PHONY: test-integrations-valgrind
+test-integrations-valgrind:
+	$(MAKE) -C $(TOY_INTEGRATIONSDIR) valgrind -k
+
 #TODO: mustfail tests
 
 #util targets