enhanced compile_return() to handle 'return' differently in a function block containing return variables

lib/hcl.h

@@ -151,6 +151,7 @@ enum hcl_synerrnum_t
 
 	HCL_SYNERR_BANNEDVARNAME, /* disallowed varible name */
 	HCL_SYNERR_BANNEDARGNAME, /* disallowed argument name */
+	HCL_SYNERR_BANNED,        /* prohibited */
 
 	HCL_SYNERR_ELIF,          /* elif without if */
 	HCL_SYNERR_ELSE,          /* else without if */