Can't compile on Windows

```
meson setup build --default-library=static
ninja -C build
```
Produces this result:
> [37/111] Compiling C++ object meson-out/ui@sta/windows_colordialog.cpp.obj.
> FAILED: meson-out/ui@sta/windows_colordialog.cpp.obj
> ccache c++ @meson-out/ui@sta/windows_colordialog.cpp.obj.rsp
> ../windows/colordialog.cpp: In function ‘void hsv2RGB(double, double, double, double*, double*, double*)’:
> ../windows/colordialog.cpp:90:9: warning: unused variable ‘c1’ [-Wunused-variable]
> double c1, c2;
> ^
> ../windows/colordialog.cpp:90:13: warning: unused variable ‘c2’ [-Wunused-variable]
> double c1, c2;
> ^
> ../windows/colordialog.cpp: In function ‘HWND__* replaceWithD2DScratch(HWND, int, SUBCLASSPROC, void*)’:
> ../windows/colordialog.cpp:868:43: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
> return newD2DScratch(parent, &r, (HMENU) id, subproc, (DWORD_PTR) data);
> ^
> ../windows/colordialog.cpp: In function ‘double editDouble(HWND)’:
> ../windows/colordialog.cpp:1022:13: error: ‘_wtof’ was not declared in this scope
> d = _wtof(s);
> ^
> ../windows/colordialog.cpp: In function ‘int editInt(HWND)’:
> ../windows/colordialog.cpp:1113:13: error: ‘_wtoi’ was not declared in this scope
> i = _wtoi(s);
> ^
> [38/111] Compiling C++ object meson-out/ui@sta/windows_debug.cpp.obj.
> FAILED: meson-out/ui@sta/windows_debug.cpp.obj
> ccache c++ @meson-out/ui@sta/windows_debug.cpp.obj.rsp
> ../windows/debug.cpp: In function ‘void uiprivRealBug(const char*, const char*, const char*, const char*, const char*, va_list)’:
> ../windows/debug.cpp:70:28: error: ‘_vscprintf’ was not declared in this scope
> n = _vscprintf(format, ap2);
> ^
> ../windows/debug.cpp:76:31: error: ‘vsprintf_s’ was not declared in this scope
> vsprintf_s(msg, n, format, ap);
> ^
> [39/111] Compiling C++ object meson-out/ui@sta/windows_events.cpp.obj.
> ../windows/events.cpp: In function ‘void issueWM_WININICHANGE(WPARAM, LPARAM)’:
> ../windows/events.cpp:147:23: warning: unused variable ‘ch’ [-Wunused-variable]
> struct wininichange *ch;
> ^
> [40/111] Compiling C++ object meson-out/ui@sta/windows_fontdialog.cpp.obj.
> FAILED: meson-out/ui@sta/windows_fontdialog.cpp.obj
> ccache c++ @meson-out/ui@sta/windows_fontdialog.cpp.obj.rsp
> In file included from ../windows/fontdialog.cpp:3:0:
> ../windows/attrstr.hpp:33:7: warning: base class ‘struct IUnknown’ has accessible non-virtual destructor [-Wnon-virtual-dtor]
> class drawingEffectsAttr : public IUnknown {
> ^
> ../windows/attrstr.hpp:33:7: warning: ‘class drawingEffectsAttr’ has virtual functions and accessible non-virtual destructor [-Wnon-virtual-dtor]
> ../windows/fontdialog.cpp: In function ‘void setupInitialFontDialogState(fontDialog*)’:
> ../windows/fontdialog.cpp:440:47: error: ‘_snwprintf’ was not declared in this scope
> _snwprintf(wsize, 512, L"%g", f->params->size);
> ^
> ../windows/fontdialog.cpp: In function ‘WCHAR* uiprivFontDialogParamsToString(fontDialogParams*)’:
> ../windows/fontdialog.cpp:785:15: error: ‘_snwprintf’ was not declared in this scope
> params->size);
> ^
> [41/111] Compiling C++ object meson-out/ui@sta/windows_editablecombo.cpp.obj.
> [42/111] Compiling C++ object meson-out/ui@sta/windows_group.cpp.obj.
> ninja: build stopped: subcommand failed.
>