``Quick'', ``slow'' and ``in-place'' Gandalf routines

A convention used extensively in the linear algebra and image packages is to provide ``quick'' and ``slow'' versions of the same operation, indicating the difference using the suffices ..._q and ..._s respectively. The meanings of the suffices vary, but are one of:

1. The ``slow'' version dynamically allocates the memory to hold the result, whereas the ``quick'' version uses a pre-allocated result passed in to the function, avoiding repetitively allocating and freeing memory when the function is called several times. This is the convention used in the image package and for general size matrix and vector functions in the linear algebra package.
2. The ``slow'' version returns a structure as its result, and the ``quick'' version expects a pointer to the result structure to be passed in. This is the convention used for fixed-size matrices and vectors in the linear algebra package.

There is also a conventional ..._i suffix for operations that overwrite one of the input arguments with the result.