Fixed a bug in the simplification of LT nodes where the delta can be reduced to a Ramp. Added internal tests to exercise these cases.\n
Cleaned up LinearSolve.cpp a bit. Changed the way Scope variables are passed around to be in line with the standard method of doing this in Halide. Got rid of all the uses of match_types by using IROperators rather than explicitly constructing IR nodes. Also fixed some indentation and spacing.