winedbg: Implemented is_break_insn for x86-64 CPUs.

programs/winedbg/be_x86_64.c

@@ -176,8 +176,8 @@ static unsigned be_x86_64_is_function_return(const void* insn)
 
 static unsigned be_x86_64_is_break_insn(const void* insn)
 {
-    dbg_printf("not done is_break_insn\n");
-    return FALSE;
+    BYTE        c;
+    return dbg_read_memory(insn, &c, sizeof(c)) && c == 0xCC;
 }
 
 static unsigned be_x86_64_is_func_call(const void* insn, ADDRESS64* callee)