Add crangler man page

[tautschnig]

This was built using help2man and then manually expanded.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a 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).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[martin-cs]

Would it be possible / viable / useful / desirable to have this process automated so that command line changes are automatically documented?

[codecov]

Codecov Report

Merging #6938 (a21c446) into develop (a1ecd93) will increase coverage by 0.01%.
The diff coverage is 98.61%.

@@             Coverage Diff             @@
##           develop    #6938      +/-   ##
===========================================
+ Coverage    77.88%   77.89%   +0.01%     
===========================================
  Files         1569     1569              
  Lines       180894   180951      +57     
===========================================
+ Hits        140882   140946      +64     
+ Misses       40012    40005       -7     

Impacted Files	Coverage Δ
src/solvers/smt2_incremental/object_tracking.h	100.00% <ø> (ø)
...c/solvers/smt2_incremental/convert_expr_to_smt.cpp	88.56% <92.85%> (+0.26%)	⬆️
src/solvers/smt2_incremental/object_tracking.cpp	98.41% <100.00%> (+0.41%)	⬆️
...t/solvers/smt2_incremental/convert_expr_to_smt.cpp	99.68% <100.00%> (+<0.01%)	⬆️
unit/solvers/smt2_incremental/object_tracking.cpp	100.00% <100.00%> (ø)
...ncremental/smt2_incremental_decision_procedure.cpp	97.63% <100.00%> (+0.04%)	⬆️
src/ansi-c/c_typecheck_expr.cpp	77.26% <0.00%> (+0.22%)	⬆️
src/util/pointer_predicates.h	100.00% <0.00%> (+25.00%)	⬆️

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[tautschnig]

Would it be possible / viable / useful / desirable to have this process automated so that command line changes are automatically documented?

My take on this is as follows:

• Check completeness of help output in CI #6917 will (once I've pushed some updates living in my local clone and once it is then merged) ensure that CI jobs fail when an option is missing from either --help output or the tool's man page.
• I would like our man pages to actually become documents worth reading. Unix users know how to use man pages, and it would be a natural way for them to find out more information about a particular option of a tool. Just reformatting help output to groff does not do justice to this.

This is also why I am creating separate PRs for each man page (there are a few more to come): each of them deserves a dedicated effort.

[martin-cs]

@tautschnig both better than my idea! Thanks.