Fixed argument for gamma/lambda ignored

[mnneely]

In an error model specification, the fixed argument is ignored.

For example, proportional(5, c(0.02, 0.05, -0.0002, 0), fixed = TRUE) does not fix gamma to 5.

[mhovd]

This should be resolved once we release the latest version of PMcore, and make the necessary changes to Pmetrics!

[mhovd]

JB reports that this bug still exists in the latest version.