Hello pvk,
I assume you didn't rebuild the MSL library that supports time functions correctly since the error "mktime() gmtime() undefined" occurs.
In fact these functions are implemented in time.c and in order to use it you should set macros _MSL_OS_TIME_SUPPORT, _MSL_CLOCK_T_AVAILABLE, _MSL_TIME_T_AVAILABLE to "1" in "ansi_prefix.CF.h" and rebuild the MSL library you are using. (I'd suggest you to backup the original libs before rebuild)
Anyway there are some specific time.c related functions that needs to be implemented. The function prototypes are located in the file "time_API.h".
I would not recommend you to add the implementations into "time.c" since this file is not suited for adding the custom code.
You can add implementation of these function wherever you want but you have to always add #include <time.c>.
Stanish