Convert [4][4] matrices to [16] arrays.

Most of the code that actually uses these matrices indexes them as
 if they were a single contiguous array, and coverity produces
 reports about the resulting accesses that overflow the static
 bounds of the first row.
This is perfectly legal in C, but converting them to actual [16]
 arrays should eliminate the report, and removes a good deal of
 extraneous indexing and address operators from the code.

Change-Id: Ibda479e2232b3e51f9edf3b355b8640520fdbf23