Fix 2 instances of void* pointer arithmetic

Partially reverts 341e440c07

Let's see if this fixes the windows build on travis

ref_gl/gl_dbghulls.c

@@ -17,7 +17,7 @@ GNU General Public License for more details.
 #include "mod_local.h"
 
 #define list_entry( ptr, type, member ) \
-	((type *)((void *)(ptr) - (size_t)(&((type *)0)->member)))
+	((type *)((char *)(ptr) - (size_t)(&((type *)0)->member)))
 
 // iterate over each entry in the list
 #define list_for_each_entry( pos, head, member )			\

ref_gl/gl_sprite.c

@@ -87,7 +87,7 @@ static const dframetype_t *R_SpriteLoadFrame( model_t *mod, const void *pin, msp
 	pspriteframe->gl_texturenum = gl_texturenum;
 	*ppframe = pspriteframe;
 
-	return ( const dframetype_t* )(( const void* )pin + sizeof( dspriteframe_t ) + pinframe.width * pinframe.height * bytes );
+	return ( const dframetype_t* )(( const byte* )pin + sizeof( dspriteframe_t ) + pinframe.width * pinframe.height * bytes );
 }
 
 /*