Fix compilation for the new TBB interface

Author: hsbadr

src/options.cpp

@@ -11,7 +11,7 @@
 extern "C" SEXP defaultNumThreads() {
    SEXP threadsSEXP = Rf_allocVector(INTSXP, 1);
 #ifndef __TBB_tbb_stddef_H
-   INTEGER(threadsSEXP)[0] = tbb::global_control::default_num_threads();
+   INTEGER(threadsSEXP)[0] = tbb::global_control::max_allowed_parallelism;
 #else
    INTEGER(threadsSEXP)[0] = tbb::task_scheduler_init::default_num_threads();
 #endif