Remove no-longer-used system_symbols

[tautschnig]

This is a follow-up to the cleanup done in 2725a05. Creating a
system_symbol_libraryt every time a languaget is created (effectively everytime
from_expr is called) is costly, because of all the strings being looked up in
the string table. Furthermore this removes this undesirable dependency on
goto-prorgrams from langapi.

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• 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/
• n/a 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.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[allredj]

🚫
This PR failed Diffblue compatibility checks (cbmc commit: a086c36).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/95377889
Status will be re-evaluated on next push.
Please contact @peterschrammel, @thk123, or @allredj for support.

Common spurious failures:

• the cbmc commit has disappeared in the mean time (e.g. in a force-push)
• the author is not in the list of contributors (e.g. first-time contributors).

The incompatibility may have been introduced by an earlier PR. In that case merging this
PR should be avoided unless it fixes the current incompatibility.

[tautschnig]

@peterschrammel @thk123 @allredj is this TG failure genuine? If so, is that cleanup or a proper bunch of work to be done on the TG side?

[thk123]

Genuine failure - not immediately obvious to me how difficult it would be to resolve. It is using is_symbol_internal_symbol to filter out things like cprover_start (according to comments I wrote but don't remember). It probably isn't a lot of work but not completely trivial. Today is my last day of the year so won't get to this till the new year, is this urgent?

[tautschnig]

It is using is_symbol_internal_symbol to filter out things like cprover_start (according to comments I wrote but don't remember).

In this case you might just locally build a system_library_symbolst rather than relying on one that's stored within languaget? That's what's done in dump_c_class.h.

Urgency/scheduling all up to you, it's just noise disturbing my profiling :-)

[allredj]

🚫
This PR failed Diffblue compatibility checks (cbmc commit: ead71ee).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/96759727
Status will be re-evaluated on next push.
Please contact @peterschrammel, @thk123, or @allredj for support.

Common spurious failures:

• the cbmc commit has disappeared in the mean time (e.g. in a force-push)
• the author is not in the list of contributors (e.g. first-time contributors).

The incompatibility may have been introduced by an earlier PR. In that case merging this
PR should be avoided unless it fixes the current incompatibility.

[allredj]

🚫
This PR failed Diffblue compatibility checks (cbmc commit: 749b4dd).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/96761629
Status will be re-evaluated on next push.
Please contact @peterschrammel, @thk123, or @allredj for support.

Common spurious failures:

• the cbmc commit has disappeared in the mean time (e.g. in a force-push)
• the author is not in the list of contributors (e.g. first-time contributors).

The incompatibility may have been introduced by an earlier PR. In that case merging this
PR should be avoided unless it fixes the current incompatibility.

[thk123]

Just to say I've started looking at this now - will keep you updated.

[thk123]

Bump made - will let you know when CI passes.

[thk123]

Needed rebasing - #3916

[tautschnig]

Closing in favour #3916.