Add bytecode and disassembly support for Python 3.8.

Also fixes running pymultic from outside of its source directory.

pyc_module.h

@@ -30,10 +30,9 @@ enum PycMagic {
     MAGIC_3_5_3 = 0x0A0D0D17,
     MAGIC_3_6 = 0x0A0D0D33,
     MAGIC_3_7 = 0x0A0D0D42,
+    MAGIC_3_8 = 0x0A0D0D55,
 };
 
-#define PYC_VERSION(maj, min)  MAGIC_##maj##_##min
-
 class PycModule {
 public:
     PycModule() : m_maj(-1), m_min(-1), m_unicode(false) { }