Least squares added to tests, make arguments optional
Coverted required args to optional args defmfun weighted-linear-mfit and replaced 'parameters with 'parameters-or-size. Added print-steps options for several more examples, and put the newline at the end of the format string. Added tests; CCL 64 bit now fails one of the linear least squares (returns zeros) and the nonlinear least squares (good to 6 or so significant figures). SBCL 64: TOTAL: 1231 assertions passed, 5 failed, 0 execution errors. CCL 64: TOTAL: 1234 assertions passed, 2 failed, 0 execution errors.
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