Eager: match on last statement and use EqTest

[Cameron-Low]

This has two parts:

1. In destruct_op, the split is done on first match: I believe the desired behaviour should be last match.
2. When checking for equality of expressions/statements, use EcReduction.EqTest instead of base equality.

[strub]

@Cameron-Low How eager was working with such a bug?

[Cameron-Low]

I think just a lack of coverage and the simple usage. I was looking at some more recent examples that involved swapping while statements around when I ran into this; all the other examples were fine.

[loutr]

Nice catch! Indeed all examples and uses so far had no duplicate while/if statement on one side, and thus the choice for split_at_cpos1 was irrelevant.

[strub]

Ok for me, but add a test then. This has been unnoticed for too long.