Fix to MXS-436: https://mariadb.atlassian.net/browse/MXS-436

Added autodetection of processor cores and used it as the default if an
invalid value is used for threads.

server/include/gw.h

@@ -88,4 +88,5 @@ int  gw_getsockerrno(int fd);
 int  parse_bindconfig(char *, unsigned short, struct sockaddr_in *);
 int setipaddress(struct in_addr *, char *);
 char* get_libdir();
+long get_processor_count();
 #endif