MINOR: cfgparse: Improve error message for invalid \x sequences

This patch states the invalid \x sequence within the error message.
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 5815da0..63e150f 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -1965,7 +1965,7 @@
 						skip = 3;
 					}
 					else {
-						ha_alert("parsing [%s:%d] : invalid or incomplete '\\x' sequence in '%s'.\n", file, linenum, args[0]);
+						ha_alert("parsing [%s:%d] : invalid or incomplete '\\x' sequence '%.*s' in '%s'.\n", file, linenum, 4, line, args[0]);
 						err_code |= ERR_ALERT | ERR_FATAL;
 						goto next_line;
 					}