Update libxayagame version.

Update the libxayagame version / commit commented as being used for
the 0.3 release in configure.ac, as we need a fresh one supporting
the new REST API.

configure.ac

@@ -40,7 +40,7 @@ AS_IF([test "x$enable_slow_asserts" = "xyes"], [
 PKG_PROG_PKG_CONFIG
 
 # The official version of libxayagame used for the 3rd competition
-# is 175238c115f576ddf33bb2fd8e2fa88cb510d932.  That of Charon is
+# is c2eea2aa70f17c4bca9a85a206287183f8b6da9c.  That of Charon is
 # 5143891ac9873a21a298ac2b2a05865a50711da5.
 
 PKG_CHECK_MODULES([XAYAGAME], [libxayautil libxayagame])