Replace `.C` with `.Call`

[ms609]

Obviates need to manually maintain src/TreeTools-init.C

Will close #155

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.87%. Comparing base (f9fac2f) to head (503e6c7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #156 +/- ## ======================================= Coverage 96.86% 96.87% ======================================= Files 59 59 Lines 4663 4666 +3 ======================================= + Hits 4517 4520 +3 Misses 146 146 ```

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