Add strtok_r.c

/*

 * public domain strtok_r()

 */

#include <string.h>

char* strtok_r( char* str, const char* delim, char** nextp )

{

    char* ret;

    if( str == NULL )

    {

        str = *nextp;

    }

    str += strspn( str, delim );

    if( *str == '\0' )

    {

        return NULL;

    }

    ret = str;

    str += strcspn( str, delim );

    if( *str )

    {

        *str++ = '\0';

    }

    *nextp = str;

    return ret;

}