Add compiler format check pragma to 'proxy_error_func' and 'proxy_debug_func'

include/proxysql.h

@@ -108,6 +108,7 @@ int pkt_end(unsigned char *, unsigned int);
 int pkt_com_query(unsigned char *, unsigned int);
 enum MySQL_response_type mysql_response(unsigned char *, unsigned int);
 
+__attribute__((__format__ (__printf__, 2, 3)))
 void proxy_error_func(int errcode, const char *, ...);
 void print_backtrace(void);
 void proxy_info_(const char* msg, ...);
@@ -115,6 +116,7 @@ void proxy_info_(const char* msg, ...);
 #ifdef DEBUG
 void init_debug_struct();
 void init_debug_struct_from_cmdline();
+__attribute__((__format__ (__printf__, 7, 8)))
 void proxy_debug_func(enum debug_module, int, int, const char *, int, const char *, const char *, ...);
 void proxy_debug_get_filters(std::set<std::string>&);
 void proxy_debug_load_filters(std::set<std::string>&);