Fixed installation or update of x13 binary.

externals/x13/installx13.m

@@ -26,12 +26,21 @@ if ~exist('x13.zip','file')
     end
     unzip('x13.zip');
     if ismac()
+        if exist('./osx', 'dir')
+            rmdir('osx', 's')
+        end
         mkdir osx;
         movefile('binaries/osx/*','./osx');
     elseif isunix()
+        if exist('./linux', 'dir')
+            rmdir('linux', 's')
+        end
         mkdir linux;
         movefile('binaries/linux/*','./linux');
     elseif ispc()
+        if exist('./windows', 'dir')
+            rmdir('windows', 's')
+        end
         mkdir windows;
         movefile('binaries/windows/*','./windows');
     else

externals/x13/updatex13.m

@@ -22,4 +22,8 @@ if exist('x13.zip','file')
     delete('x13.zip')
 end
 
+if exist('./binaries', 'dir')
+    rmdir('binaries', 's');
+end
+
 installx13();
\ No newline at end of file