Reenable on-disk caching

It can still be helpful to turn them off, but now that the refcounter non-determinism
has been fixed I think it's time to have these back on.

src/codegen/parser.cpp

@@ -1238,7 +1238,6 @@ AST_Module* caching_parse_file(const char* fn, FutureFlags inherited_flags) {
         FileHandle cache_fp(cache_fn.c_str(), "r");
         if (cache_fp) {
             while (true) {
-                break; // XXX JUST FOR TESTING
                 int read = fread(buf, 1, 1024, cache_fp);
                 file_data.insert(file_data.end(), buf, buf + read);
 

src/core/options.cpp

@@ -81,7 +81,7 @@ bool ENABLE_REOPT = 1 && _GLOBAL_ENABLE;
 bool ENABLE_PYSTON_PASSES = 0 && _GLOBAL_ENABLE;
 bool ENABLE_TYPE_FEEDBACK = 1 && _GLOBAL_ENABLE;
 bool ENABLE_RUNTIME_ICS = 1 && _GLOBAL_ENABLE;
-bool ENABLE_JIT_OBJECT_CACHE = 0 && _GLOBAL_ENABLE;
+bool ENABLE_JIT_OBJECT_CACHE = 1 && _GLOBAL_ENABLE;
 bool LAZY_SCOPING_ANALYSIS = 1;
 
 bool ENABLE_FRAME_INTROSPECTION = 1;