Implement fetching bold kerning

C doesn't have function overloading, so I had to resort to function name
signature changes to resemble overloading. I think this is an ok way to
do this

src/SFML/Graphics/Font.cpp

@@ -121,6 +121,13 @@ float sfFont_getKerning(const sfFont* font, sfUint32 first, sfUint32 second, uns
 }
 
 
+////////////////////////////////////////////////////////////
+float sfFont_getBoldKerning(const sfFont* font, sfUint32 first, sfUint32 second, unsigned int characterSize)
+{
+    CSFML_CALL_RETURN(font, getKerning(first, second, characterSize, true), 0);
+}
+
+
 ////////////////////////////////////////////////////////////
 float sfFont_getLineSpacing(const sfFont* font, unsigned int characterSize)
 {