Add explicit cast to silence C++14 -Wnarrowing conversion warnings.
See also: https://bugs.gentoo.org/show_bug.cgi?id=600298

--- a/src/xsb_level.cpp
+++ b/src/xsb_level.cpp
@@ -784,7 +784,7 @@
 
 bool FromXyeDFS(int* mem, unsigned char x, unsigned char y)
 {
-    static const unsigned char dx[4] = {0,0,-1,1}, dy[4] = {-1,1,0,0};
+    static const unsigned char dx[4] = {0,0,(unsigned char)-1,1}, dy[4] = {(unsigned char)-1,1,0,0};
     int &res =  mem[y*XYE_HORZ+x];
     if( res==0)
     {