Preliminary reworking of value-binding logic in RegionStore:
Preliminary reworking of value-binding logic in RegionStore:

(1) Introduce a new 'BindingKey' class to match 'BindingValue'.  This
gives us the flexibility to change the current key value from 'const
MemRegion*' to something more interesting.

(2) Rework additions/removals/lookups from the store to use new
'Remove', 'Add', 'Lookup' utility methods.

No "real" functionality change; just prep work and abstraction.


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@93136 91177308-0d34-0410-b5e6-96231b3b80d8

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