changed solveLinear interface for mutable matrices.
--enable-flint still needed.

This commit is a first run at making sure M2 can compile without flint.
But it is not yet working (works fine if flint is enabled).
added MutableMatrix ^ ZZ to mutable mat.m2
Added ARingQQGMP, and made it hopefully easy to switch between gmp/flint versions
changed some header includes related to aring-qq
working with Jakob.  Changed lin alg interface, working on tests and
generally getting it functional.
updated testAddMultipleTo
Merge branch 'linalg' of https://github.com/mikestillman/M2 into linalg
implemented addMultipleTo and subtractMultipleTo for FFPACK field