Inlined purge_kernel_caches()

refs #58
Include everything inside multiple_objects test sources

Optimization in d6e549e5063e5793ab38ccf9b4b1dd9414472346 should not
apply for this test.

refs #58
Inlined detail::empty_state()

refs #58
Allow vector valued matrices and vectors in spmv

Makes the following possible:

    vex::SpMat <cl_double2> A;
    vex::vector<cl_double2> x, y;
    y = A * x;
Reformulated test condition in multivector_arithmetics
Revert "Reformulated test condition in multivector_arithmetics"

This reverts commit dd610aaa54e93a7c29056b3f5362f64902b1354f.
More meaningful test in multivector_arithmetics
Move AMD to the end of the tested platforms list

It fails too often
Merge remote-tracking branch 'upstream/master'