Non SIMD folding combos cause error

Combining a folding spec with the 'intel64' arch spec will cause a failure during var initialization. This combo of features triggers intrinsic emulation and is probably not practically useful, but it is allowed.

make clean; make -j real_bytes=8 use_rcp=0 allow_new_var_types=0 trace=1 yc-and-yk-test stencil=test_2d arch=intel64 fold=x=3,y=2 YK_CXXOPT=-O0 mpi=0
...
Initializing stencil vars...
sh: line 1: 834445 Segmentation fault