Fixing RETVAL code.
Fixing RETVAL code.

-RETVAL was getting None value because greenlet_entry should be
 returning the value.

-Also, printing the return of switch with str() could cause an infinite
 loop case the value is a recursive structure as it is sometimes the case.

thiago-silva/memetalk,memetalk/memetalk,thiago-silva/memetalk,thiago-silva/memetalk,memetalk/memetalk,memetalk/memetalk