gdi32: Move 16-bit functions not exported in gdi32.dll into files compiled only when 16-bit functionality is enabled.

wineoss.drv: Use CP_UNIXCP instead of CP_ACP for converting strings that come from system library functions or system headers.

widl: Fix typos in write_remoting_arg which caused ref pointers to unions to not result in direct calls to NonEncapsulatedUnion/EncapsulatedUnion functions.

With thanks to Dmitry for spotting this.

user32/tests: Ignore SPI_ICONVERTICALSPACING notifications. Don't reset mouse buttons if setting failed.

gdi32/tests: From Vista onwards TabbedTextOut ignores justification, so remove that bit of the test.

- dwInstance and dwDriver are a DWORD_PTR.
- acmF*Enum functions take a DWORD_PTR as 4th parameter.
- The last parameter of SendDlgItemMessage and MSACM_Message is a
  LPARAM.

Fixes 63 Win64 compile warnings.

gdi32: The special handling of the character codes metrics for symbol fonts should be based on the presence of the MS symbol charmap rather than whether the font is enumerated as SYMBOL_CHARSET.

GdipCreateBitmapFromHBITMAP currently assumes that all bitmaps are
top-down, even though a positive height (which it also assumes)
signals a bottom-up DIB. The net result is that
GdipCreateBitmapFromHBITMAP flips images vertically.

We need to take into account the trailing NULL in envp.