Use a larger buffer so long version numbers don't overflow the protocol parser

--- a/src/include/pgagroal.h
+++ b/src/include/pgagroal.h
@@ -67,7 +67,7 @@ extern "C" {
 
 #define MAX_BUFFER_SIZE      65535
 #define DEFAULT_BUFFER_SIZE  65535
-#define SECURITY_BUFFER_SIZE   512
+#define SECURITY_BUFFER_SIZE  1024
 
 #define MAX_USERNAME_LENGTH   128
 #define MAX_DATABASE_LENGTH   256
