lstsq: explain singular values better

Author: perazz

doc/specs/stdlib_linalg.md

@@ -777,8 +777,7 @@ Result vector `x` returns the approximate solution that minimizes the 2-norm \(
 
 `cond` (optional): Shall be a scalar `real` value cut-off threshold for rank evaluation: `s_i >= cond*maxval(s), i=1:rank`. Shall be a scalar, `intent(in)` argument.
 
-`singvals` (optional): Shall be a `real` rank-1 array of the same kind `a` and size at least `m
-al(shape(a))`, returning the list of singular values `s(i)>=cond*maxval(s)`, in descending order of magnitude. It is an `intent(out)` argument.
+`singvals` (optional): Shall be a `real` rank-1 array of the same kind `a` and size at least `min(m,n)`, returning the list of singular values `s(i)>=cond*maxval(s)` from the internal SVD, in descending order of magnitude. It is an `intent(out)` argument.
 
 `overwrite_a` (optional): Shall be an input `logical` flag. If `.true.`, input matrix `A` will be used as temporary storage and overwritten. This avoids internal data allocation. This is an `intent(in)` argument.