Fix compile error for libretro, and minor warnings from clang.

src/common/FBBackendSDL2.hxx

@@ -112,9 +112,7 @@ class FBBackendSDL2 : public FBBackend
       { return SDL_MapRGB(myPixelFormat, r, g, b); }
 
     inline uInt32 mapRGBA(uInt8 r, uInt8 g, uInt8 b, uInt8 a) const override
-    {
-      return SDL_MapRGBA(myPixelFormat, r, g, b, a);
-    }
+      { return SDL_MapRGBA(myPixelFormat, r, g, b, a); }
 
     /**
       This method is called to get a copy of the specified ARGB data from the

src/emucore/FrameBuffer.cxx

@@ -1422,8 +1422,7 @@ bool FrameBuffer::loadBezel()
 
   if(isValid)
   {
-    const float overscan = 1 - myOSystem.settings().getInt("tia.fs_overscan") / 100.0;
-    bool fs = fullScreen();
+    const float overscan = 1 - myOSystem.settings().getInt("tia.fs_overscan") / 100.F;
 
     uInt32 imageW, imageH;
     if(fullScreen())
@@ -1469,15 +1468,16 @@ float FrameBuffer::maxWindowZoom() const
   float multiplier = 1;
 
   const bool showBezel = myOSystem.settings().getBool("bezel.show");
-  const double scaleW = showBezel ? (16. / 9.) / (4. / 3.) : 1; // = 1.333
+  const float scaleW = showBezel ? (16.F / 9.F) / (4.F / 3.F) : 1.F; // = 1.333
 
   for(;;)
   {
     // Figure out the zoomed size of the window
     const uInt32 width  = TIAConstants::viewableWidth * multiplier * scaleW;
     const uInt32 height = TIAConstants::viewableHeight * multiplier;
 
-    if((width > myAbsDesktopSize[display].w) || (height > myAbsDesktopSize[display].h))
+    if((width > myAbsDesktopSize[display].w) ||
+       (height > myAbsDesktopSize[display].h))
       break;
 
     multiplier += ZOOM_STEPS;

src/emucore/FrameBuffer.hxx

@@ -467,7 +467,7 @@ class FrameBuffer
       Return bezel names, which are either read from the properties
       or generated from the cart name.
 
-      @param   The index of the returned bezel name
+      @param index  The index of the returned bezel name
 
       @return  The bezel name for the given index
     */

src/os/libretro/FBBackendLIBRETRO.hxx

@@ -47,6 +47,9 @@ class FBBackendLIBRETRO : public FBBackend
     uInt32 mapRGB(uInt8 r, uInt8 g, uInt8 b) const override {
       return (r << 16) | (g << 8) | b;
     }
+    uInt32 mapRGBA(uInt8 r, uInt8 g, uInt8 b, uInt8 a) const override {
+      return (a << 24) | (r << 16) | (g << 8) | b;
+    }
 
     /**
       This method is called to query and initialize the video hardware