implemented jump table dispatch

- currently only enabled on supported platforms (GNU C Compiler + Clang)
- when enabled, sped up examples/fibtest.cosmo by about 20% (avg of 11.179s prior and 8.799 after)

NOTE: malicious dumps can trivially cause crashes now by having junk function chunks

src/coperators.h

@@ -64,7 +64,7 @@ typedef enum
     OP_FALSE,
     OP_NIL,
 
-    OP_RETURN
+    OP_RETURN,
 } COPCODE; // there can be a max of 256 instructions
 
 #endif