Revert changes on memcpy matrix getters

Fix issue #133

The C memcpy was replaced by loops, but it causes the kernel to segfault
during SP analysis with Noise.

memcpy is good with POD and tends to be inlined [1].
Replacement candidate is std:copy. Please provide testcase and
testbench.

[1] http://nadeausoftware.com/articles/2012/05/c_c_tip_how_copy_memory_quickly