configure.ac: check libopts version more strictly
This is a continuation of the discussion in: !808 (comment 124782407)
In libopts there are two places where library versions are checked: at source code level and binary level.
These are basically the same condition, but we can't do much about the latter (e.g., copying a linked binary to older distributions).
Checklist
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Code modified for feature -
Test suite updated with functionality tests -
Test suite updated with negative tests -
Documentation updated / NEWS entry present (for non-trivial changes)
Reviewer's checklist:
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Any issues marked for closing are addressed -
There is a test suite reasonably covering new functionality or modifications -
Function naming, parameters, return values, types, etc., are consistent and according to CONTRIBUTION.md
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This feature/change has adequate documentation added -
No obvious mistakes in the code