Upstream string format verification tests

[peterschrammel]

Includes a required java-models-library update diffblue/java-models-library#25

• Each commit message has a non-empty body, explaining why the change was made.
• 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).
• My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: 29d4b46).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/114878566

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (develop@86499a6). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             develop    #4768   +/-   ##
==========================================
  Coverage           ?   68.58%           
==========================================
  Files              ?     1275           
  Lines              ?   105032           
  Branches           ?        0           
==========================================
  Hits               ?    72036           
  Misses             ?    32996           
  Partials           ?        0

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[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: f65b0db).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/114923286