Fixing arrays hashing.

To avoid having the same hashes for variables like a[10] and a1[0]
array boundary hash moved above index hashing.
Test case testing multi-index array hashing updated.

Now cases like a[10] and a1[0] covered while checking if hashing is
working accurately.
Fix test relying on ordering of array elements returning by mergedata.

This one is simple change of expected strings. We can think how to modify
this test in future to sort the merged array elements before comparing.
Merge pull request #2036 from pasinskim/redmine_6674

Fixing arrays hashing.