tweak the tests a bit

[KristofferC]

• Avoid using eval to get the Base and IntelVectorMath function, just give the actual module in the variable base_unary_real and use getproperty instead.
• Make some more things const.
• Use parentmodule to check the module instead of the slightly more convoluted way with which.
• Create some helper variables at the beginning of the loop body to simplify some of the expressions later (since the same expression is used many times).