Update jbmc/lib/java-models-library for PR16 (getChars) and activate Tests

[romainbrenguier]

diffblue/java-models-library#16

• Each commit message has a non-empty body, explaining why the change was made.
• [na] Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• [na] My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• [na] White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: a2f8fb3).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/92481187

[peterschrammel]

Tagging Do not merge because the java-models-library pointer needs to be updated before merging.

[romainbrenguier]

Now pointing to master

[tautschnig]

@romainbrenguier This is now failing CI.

[romainbrenguier]

This is caused by the first commit diffblue/java-models-library#13 (also brought with this submodule update).
I suspect the CASE_INSENSITIVE_ORDER field.

[romainbrenguier]

Superseded by #4476

[tautschnig]

Closing as #4476 has been merged.