Implement dynamic run-time check for L1 and L2 cache size

[Martin Albrecht]

The static checks in the autoconf script are not cross platform and assume knowledge about the CPU. As an alternative we should implement run-time checks for L1 and L2 (or L3) which can be used instead of the static compile-time checks. If those work well, we should use them at compile time to figure out L1 and L2.

[Martin Albrecht]

This has been implemented; though we only run the detection at compile time.