Fix `drawCircle` signature in `PaintingWindow`.
Change signature of painting commands, update doc, hide functions using Qt objects.
Add unit tests for painting commands.
Fix wrong variable name.
Fix miscellaneous compiler warnings.
Remove obsolete painting function.
Add a precision on the usage of DO_STATIC_ASSERT.
Merge branch 'fix-miscellaneous-compiler-warnings' of ssh://github.com/DO-CV/DO-CV into fix-miscellaneous-compiler-warnings
Revert "Fix `drawCircle` signature in `PaintingWindow`."

This reverts commit bfc4b49dff33c48682b8c8d97afde39ef7db6758.
Revert "Change signature of painting commands, update doc, hide functions using Qt objects."

This reverts commit d14cc4c2cd5228d7d99477833a36829a4885931a.
Revert "Fix wrong variable name."

This reverts commit aebeb0b4fe2191a2e54d64adfb1138e4103d09be.
Revert "Remove obsolete painting function."

This reverts commit bde57b76411e9cbbbada54ab9394339050e20d75.
Revert "Add unit tests for painting commands."

This reverts commit cadee18613b145dbf5a4e591819e7defaa076dc6.
Disable the too verbose `-Wundef` compiler flags.
Remove unnecessary `const` qualifiers.
Merge pull request #77 from DO-CV/fix-miscellaneous-compiler-warnings

[MAINT] Fix miscellaneous compiler warnings.