Move software renderer into its own namespace to isolate its globals and make

any access explicit. This reveals the places in the code where they are being
accessed where they shouldn't and prevents accidental usage.

src/r_swrenderer.cpp

@@ -58,11 +58,18 @@ CUSTOM_CVAR(Bool, r_polyrenderer, 0, CVAR_ARCHIVE | CVAR_GLOBALCONFIG | CVAR_NOI
 	}
 }
 
+namespace swrenderer       
+{
+
 void R_SWRSetWindow(int windowSize, int fullWidth, int fullHeight, int stHeight, float trueratio);
 void R_SetupColormap(player_t *);
 void R_SetupFreelook();
 void R_InitRenderer();
 
+}
+
+using namespace swrenderer;
+
 FSoftwareRenderer::FSoftwareRenderer()
 {
 }