Bug in main SVD wrapper

The line

https://git.fmrib.ox.ac.uk/fsl/armawrap/-/blob/master/armawrap/function_svd.hpp#L25

resizes U to the dimensions of At ( the input Data ). However this will crash for over-complete matrices ( e.g. 12x10 ). This line may have originally been introduced when the function used arma:svd for compatibility with the newmat interface. However svd_econ appears to always output a U of the expected size, including for the case of an over-complete input ( 12x10 -> 10x10 ). One fix would be to make the first limit min(At.n_rows-1, At.n_cols-1) but it may be simpler to just drop the submatrix call - perhaps avoid the copy altogether and pass U straight in, setting U=0 if !withU similar to V.