add some special tests for muls
_mm_mul_epi32 needs deinterleaving for correct ordering of results in split_multiplies
add split_multiplies unit test, fix problems with other variants of split_multiplies
#421: temporarily disable special saturation-handling code in muls for since group currently saturates because of issue #166
fix imaginary/real multiplication
fix scalar_of include in compare_* functions
fix compilation of call to report_ulp_unit_error