Revert "Merge pull request #191 from Reinis/arma_no_wrapper"

This reverts commit 5ed90a02f0196b790d969b2f26dfc7a3462f453b, reversing
changes made to aeccee21a18a8326fb3868dc1745b5e6d266e67c.

I was pointed out that armadillo-4 already has this implemented with
ARMA_DONT_USE_WRAPPER.