1. Introduce CExportFiles class
This class aggregates all files that are created specifically for
C export. Adding more such classes for other output kinds should
help getting rid of OutputFiles class.
2. Remove NativeGenerationState.tempFiles
Making NativeGenerationState (and compiler phases in general)
unaware of files and their lifetime is necessary for making phases
simpler and easier to compose.
Sergey Bogolepov
f7d3312ad5