Reordered the functions in ExtCore.String, but didn't change any functionality.
Moved the BitOps and PatriciaTrieConstants modules from Collections.IntMap.fs to Collections.IntSet.fs so we could move IntSet above IntMap in the project; this allows us to implement some additional operations on IntMap which need to use IntSet.
Implemented some (but not all) unit tests for the ExtCore.Collections.IntMap module.
Implemented more test cases for IntMap, and made the existing tests more robust.
Reordered the functions in the IntMap module to group them by functionality.
Changed the compiled name of 'iter' functions to "Iter" (instead of "Iterate"), and 'init' functions to "Init" (instead of "Initialize") to match FSharp.Core.
Fixed the 'add' and 'remove' tests (there was a copy-paste error).
Miscellaneous minor tweaks; committing before branching to fix a bug in IntMap.