Working pgAdmin3 update for WX Widgets 3.2 (dogfooded on MinGW64)

[asctime]

https://github.com/asctime/pgadmin3

This is a working forward-port first draft of pgAdmin III 1.22 to wxWidgets 3.2, dogfooded on Windows using the MSYS2 MinGW64 toolchain. The update primarily addresses API removals and compatibility changes between the older wxWidgets code and wxWidgets 3.2, including migration of legacy wxList/wxNode iteration to wxList::compatibility_iterator, updated wxString character-buffer handling, wxUtfFile and Win32 API calls requiring explicit character pointers, removal of obsolete wxString-to-LPCTSTR casts, and associated resource/compiler compatibility fixes. The port also includes a PostgreSQL/libpq compatibility guard around PQmblenBounded and a windres-compatible Windows version resource definition. The existing pgAdmin3 architecture and functionality are otherwise retained; the goal is a practical wxWidgets 3.2 build rather than a broader codebase refactor.