Wraps TTF_GetFontKerningSize (from SDL_ttf 2.0.18) to get the kerning between two glyphs in the dsdl2.ttf.Font
preceeding dchar glyph
dchar glyph
kerning between prevGlyph and glyph
See Implementation
Wraps TTF_GetFontKerningSize (from SDL_ttf 2.0.18) to get the kerning between two glyphs in the dsdl2.ttf.Font