Native Windows Folder picker

[machcnz]

PS/Cmd shell file picker would intermittently not work. This pull request switches to native Win32 file/folder picker.

Changes:

1. meson.build: ln 368: gui_ldflags += ['-lmf', '-lmfplat', '-lmfuuid', '-lmfreadwrite', '-lole32', '-lavrt', '-lksuser', '-luuid', '-lshell32']
2. gui_settings.c
   #else
   #include <direct.h>
   #define COBJMACROS
   #define INITGUID
   #define Rectangle Win32_Rectangle
   #define CloseWindow Win32_CloseWindow
   #define ShowCursor Win32_ShowCursor
   #include <shlobj.h>
   #include <shobjidl.h>
   #undef ShowCursor
   #undef CloseWindow
   #undef Rectangle
   #endif

---

3. gui_settings.c replace ps file picker:
   #elif defined(_WIN32) || defined(_WIN64)
   // Native Win32 file picker - no PowerShell, no console required
   OPENFILENAMEA ofn = {0};
   ofn.lStructSize = sizeof(ofn);
   ofn.lpstrFilter = "FLAC files\0*.flac\0All files\0*.*\0";
   ofn.lpstrFile = picked;
   ofn.nMaxFile = sizeof(picked);
   ofn.lpstrTitle = "Select FLAC playback file";
   ofn.Flags = OFN_FILEMUSTEXIST | OFN_PATHMUSTEXIST;
   GetOpenFileNameA(&ofn);
   trim_newlines(picked);