tests: fix TestSortValues on 32-bits platforms

reflect.DeepEqual fails when comparing reflect.Value containing float64. I
think it cannot make sense of reflect.Value pointer tricks and directly
compare reflect.Value.val fields which contain the float value in 64 bits,
but a pointer to the float in 32 bits.

Fortunately, interface{} which have a similar memory layout, compare correctly,
so we just turn the []reflect.Value into []interface{}.
Merge pull request #14 from pmezard/fix-sorting-test-on-32bits

tests: fix TestSortValues on 32-bits platforms