Implement and test GdiGetCharDimensions.

include/wingdi.h

diff --git a/include/wingdi.h b/include/wingdi.h
index cb429ac..f4ae99d 100644
--- a/include/wingdi.h
+++ b/include/wingdi.h
@@ -3335,6 +3335,7 @@
 BOOL      WINAPI GdiComment(HDC,UINT,const BYTE *);
 DEVMODEW * WINAPI GdiConvertToDevmodeW(const DEVMODEA *);
 BOOL      WINAPI GdiFlush(void);
+LONG      WINAPI GdiGetCharDimensions(HDC, LPTEXTMETRICW, LONG *);
 BOOL      WINAPI GdiGradientFill(HDC,PTRIVERTEX,ULONG,PVOID,ULONG,ULONG);
 BOOL      WINAPI GdiIsMetaFileDC(HDC);
 BOOL      WINAPI GdiIsMetaPrintDC(HDC);