Minor cleanup in studies/amr
Merge pull request #612 from vasslitvinov/minor-studies/amr-cleanup

Minor cleanup in studies/amr.

* Changed 'var' -> 'ref' for the return intent of a proc.

* In proc =(T,a), give T the 'ref' intent.

This proc accepts tuples, and tuples are currently passed by ref
for blank intent, so 'ref' is not needed. However, the compiler
warns that = does not have the canonical 'ref' on the first argument.
So adding 'ref' eliminates the warning.