Fix nested pre-processor blocks

[albertziegenhagel]

In the pre-processor code, when we check whether a #define or #include statement should be evaluated, only the top of the pre-processor stack was taken into account. This commit changes it so that all the previously taken branches need to evaluate to true.

Fixes #404.

[codecov[bot]]

Codecov Report

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

Project coverage is 88.24%. Comparing base (81a33a1) to head (7c24d0c).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #405 +/- ## ======================================= Coverage 88.23% 88.24% ======================================= Files 35 35 Lines 4795 4796 +1 ======================================= + Hits 4231 4232 +1 Misses 564 564 ```

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