Minor refactoring, added OP_GETMETHOD

You can use ':' without invoking. So you can grab a method binding to an object and later call it. Also some GC bugs were fixed.

A new preprocessor macro (VM_DEBUG) has been added. Defining this macro will print each instruction thats being executed in the VM, as
well as print each call.

src/cdebug.h

@@ -6,4 +6,6 @@
 COSMO_API void disasmChunk(CChunk *chunk, const char *name, int indent);
 COSMO_API int disasmInstr(CChunk *chunk, int offset, int indent);
 
+void printIndent(int indent);
+
 #endif