Fixes and improvements

[MisakaVan]

This pull request includes several changes to improve identifier management and error handling in the codebase, as well as updates to documentation and test files. The most important changes include modifying how identifiers are registered and checked, updating the documentation to reflect these changes, and adding new test cases to ensure the correctness of the implementation.

Identifier Management and Error Handling:

• src/lang.c: Replaced check_identifier_* functions with register_identifier_* functions to ensure identifiers are registered correctly when defining structs, unions, and enums. [1] [2] [3]
• src/lib.c: Updated conflict_identifier_register_lut to reflect the correct conflict rules between struct, union, and enum names. Added suggestions in check_identifier_in_table function to guide users on correct identifier usage. [1] [2]

Documentation Updates:

• doc/parser.md: Added a new section on unresolved issues related to identifier management and updated the description of how struct/union/enum identifiers are handled. [1] [2]

Test File Updates:

• resource/test/test-identifier-predeclared/testcase1.jtl.h: Added a warning comment for typedef usage to reflect the new identifier management rules.
• resource/test/test-identifier-predeclared/testcase2.jtl.h: Added new test cases to check the correct handling of struct and enum identifiers.

Script Updates:

• batchtest.sh: Modified the script to run tests only on files with the .jtl.h extension by introducing a new inputext variable. [1] [2]