[BUG] Invalid version header for project name not valid as a C identifier

[arnaud-m]

Describe the bug
The generated version.hpp is invalid when the project name is not a valid C identifier.
For example, project names containing dashes (-) result in invalid C symbols.

In addition, the generated version.hpp is not added to the include path, which makes it unusable from within the project itself.

To Reproduce
Steps to reproduce the behavior:

1. Change the project name from 'Project' to 'Project-name-with-dashes'
2. Copy cmake/ProjectConfig.cmake.in to Project-name-with-dashesConfig.cmake.in
3. make test
4. Inspect the generated header in build/include/project-name-with-dashes
5. Try to include 'version.hpp' from the project source.

Expected behavior

• The project name should be transformed into a valid C identifier when generating version.hpp.
• The generated header should be added to the project's include path for the library and executable.