plugin: restore IDA 9.0 compatibility

[Oxygen1a1]

Summary

Fix plugin compatibility with IDA 9.0 and other pre-9.2 SDK/runtime combinations.

The previous Windows plugin build could import idaplace_t__equals, which is exported by newer IDA versions but not
by IDA 9.0. This caused the plugin DLL to fail loading before initialization on IDA 9.0.

Changes

• Add a local compatibility shim for idaplace_t__equals
• Add SDK-version guards for IDA 9.0 API differences:
  • open_database()
  • is_ida_library()
  • callcnv_t
  • HTI_SEMICOLON
  • GENDSM_UNHIDE
  • enum member lookup helpers
  • Hex-Rays ctree parent access
  • BWN_TITREE
• Keep existing behavior for newer SDKs

Validation

• Built idasql_plugin with IDA SDK 9.0, MCP enabled
• Built idasql_plugin with IDA SDK 9.2
• Built idasql_plugin with IDA SDK 9.3
• Checked generated DLL imports against IDA 9.0.24.0925 ida.dll: 0 missing imports
• Confirmed idaplace_t__equals is no longer imported
• Verified LoadLibrary succeeds against the local IDA 9.0 setup directory