Fix 'unused parameter' warning.
Reset the dirty-bit of the buffer after sync()ing.
Update the shader_pipeline code generator.

It now only uses local copies of variables when needed.

This makes the generated shaders more readable, and allows the user to
use non-copyable types like sampler2D.
Add warning-flags and fix some small warnings.
Fix compile error in vao::attribute.
Make parameter 'offset' of vao::attribute a const pointer.
Add missing 'inline' keyword in xxx/import/assimp.hpp.
Rename 'near' and 'far', since they are reserved on some platforms.
Use GL_ARRAY_BUFFER instead of GL_COPY_WRITE_BUFFER for OSX.
Include <cmath> in matrix.hpp.
Fix from_columns an from_rows in matrix.hpp.

It didn't work if the rows or columns weren't of the same length.
Include <cmath> in transformation.hpp.