Memory leak on task deletion with configUSE_NEWLIB_REENTRANT

IMO, standard newlib uses too much RAM for an ARM Cortex based system if you enable configUSE_NEWLIB_REENTRANT. So we don’t use configUSE_NEWLIB_REENTRANT. Instead, we replace the functions that use the newlib reent struct. The main ones are printf, strtod and functions related to these. Some other functions that use the reent struct have alternatives that don’t, for example we use gmtime_r instead of gmtime.