Optimise the RGB to pixel conversion to simple shifts

Might as well make it inline at this point as well as it is used
heavily in other routines that convert entire blocks of pixels.
diff --git a/common/rfb/PixelFormat.h b/common/rfb/PixelFormat.h
index e05e6f9..fdb829c 100644
--- a/common/rfb/PixelFormat.h
+++ b/common/rfb/PixelFormat.h
@@ -59,8 +59,8 @@
     inline Pixel pixelFromBuffer(const rdr::U8* buffer) const;
     inline void bufferFromPixel(rdr::U8* buffer, Pixel pixel) const;
 
-    Pixel pixelFromRGB(rdr::U16 red, rdr::U16 green, rdr::U16 blue, ColourMap* cm=0) const;
-    Pixel pixelFromRGB(rdr::U8 red, rdr::U8 green, rdr::U8 blue, ColourMap* cm=0) const;
+    inline Pixel pixelFromRGB(rdr::U16 red, rdr::U16 green, rdr::U16 blue, ColourMap* cm=0) const;
+    inline Pixel pixelFromRGB(rdr::U8 red, rdr::U8 green, rdr::U8 blue, ColourMap* cm=0) const;
 
     void bufferFromRGB(rdr::U8 *dst, const rdr::U8* src, int pixels, ColourMap* cm=0) const;
     void bufferFromRGB(rdr::U8 *dst, const rdr::U8* src, int w, int pitch,