This patch allows GORI to recognize and pass relations along the 
calculation chain.  This will allow relations between the LHS and the 
operand being calculated to be utilized in op1_range and op2_range.

compute_operand_range will look to see if the current statement creates 
a relation between op1 and op2, and if it does, creates a relation 
record and a passes it down to the next routine.
Ie:

[0,0] = a_1 < b_2

would create a relation record for (a_1 >= b2) and pass it along the 
calculation chain to the various op1/op2 ranges for use in their 
calculations.  This patch merely creates and passes it around, it 
doesn't actually do anything with it yet.

Bootstrapped on x86_64-pc-linux-gnu with no regressions.  Pushed.

Andrew