Overhaul sprand, sprandn functions. * __sprand_impl__: Rename variable "funname" to "fcnname". Add comments to Reciprocal Condition number calculation. Rename "mynnz" to "k" to match rest of code. Add input validation test that RC is scalar or vector. Use double quotes instead of single quotes per Octave guidelines. Check for special case of output vector to avoid problems. Use randperm to replace do/until loop for speed. Pre-calculate speye() value instead of doing per loop iteration. * sprand.m: Improve docstring. Match function output variable name to documentation. Add check string to %!error tests. * sprandn.m: Improve docstring. Match function output variable name to documentation. Add check string to %!error tests.