Internal function to converts a clock model
to the `prior`

section of the XML as text

```
clock_model_to_xml_prior_distr(
inference_model,
clock_model = "deprecated",
mrca_priors = "deprecated",
tipdates_filename = "deprecated"
)
```

## Arguments

- inference_model
a Bayesian phylogenetic inference model.
An inference model is the complete model setup in which a site model,
clock model, tree prior and more are specified.
Use create_inference_model to create an inference model.
Use check_inference_model to check if an inference model is valid.
Use rename_inference_model_filenames to rename the files in an
inference model.

- clock_model
a clock model,
as returned by `create_clock_model`

- mrca_priors
a list of one or more Most Recent Common Ancestor priors,
as returned by `create_mrca_prior`

- tipdates_filename
name of the file containing the tip dates.
This file is assumed to have two columns, separated by a tab.
The first column contains the taxa names, the second column contains
the date.

## Value

a character vector of XML strings

## Author

Richèl J.C. Bilderbeek

## Examples

```
# <distribution id="posterior" spec="util.CompoundDistribution">
# <distribution id="prior" spec="util.CompoundDistribution">
# HERE, where the ID of the distribution is 'prior'
# </distribution>
# <distribution id="likelihood" ...>
# </distribution>
# </distribution>
```