Fixed text rendering artifacts on Radeon cards.

Padding set to 1.0 was causing adjacent glyphs leaking on Radeon cards. The initial padding value for glyphs was too high anyway, the proper value should be 0.5 on each side.

src/SFML/Graphics/Text.cpp

@@ -50,7 +50,7 @@ namespace
     // Add a glyph quad to the vertex array
     void addGlyphQuad(sf::VertexArray& vertices, sf::Vector2f position, const sf::Color& color, const sf::Glyph& glyph, float italicShear, float outlineThickness = 0)
     {
-        float padding = 1.0;
+        float padding = 0.5;
 
         float left   = glyph.bounds.left - padding;
         float top    = glyph.bounds.top - padding;