Fixes -Wsign-compare

See #2613

src/graphics/irr_driver.cpp

@@ -1600,7 +1600,7 @@ std::string IrrDriver::getSmallerTexture(const std::string& filename)
         {
             core::dimension2d<u32> dim = img->getDimension();
             core::dimension2d<u32> new_dim; // Dimension of the cached texture
-            const int scale_factor = 2;
+            const unsigned scale_factor = 2;
             // Resize the texture only if it can be done properly
             if (dim.Width < scale_factor || dim.Height < scale_factor)
                 new_dim = dim;

src/states_screens/credits.cpp

@@ -215,7 +215,7 @@ void CreditsScreen::loadedFromFile()
 
 
     irr::core::stringw translators_credits = _("translator-credits");
-    const int MAX_PER_SCREEN = 6;
+    const unsigned MAX_PER_SCREEN = 6;
 
     if (translators_credits != L"translator-credits")
     {

src/tracks/check_line.cpp

@@ -30,6 +30,7 @@
 #include "irrlicht.h"
 
 #include <algorithm>
+#include <cstdint>
 #include <string>
 
 /** Constructor for a checkline.
@@ -171,7 +172,7 @@ bool CheckLine::isTriggered(const Vec3 &old_pos, const Vec3 &new_pos,
 
     bool previous_sign;
 
-    if (kart_index == -1)
+    if (kart_index == UINT_MAX)
     {
         core::vector2df p = old_pos.toIrrVector2d();
         previous_sign = (m_line.getPointOrientation(p) >= 0);
@@ -212,10 +213,10 @@ bool CheckLine::isTriggered(const Vec3 &old_pos, const Vec3 &new_pos,
     else
         result = false;
 
-    if (kart_index != -1)
+    if (kart_index != UINT_MAX)
         m_previous_sign[kart_index] = sign;
 
-    if (result && kart_index != -1)
+    if (result && kart_index != UINT_MAX)
     {
         LinearWorld* lw = dynamic_cast<LinearWorld*>(w);
         if (lw != NULL)