fix issue #220: implicit declaration of function ‘isatty’

Fixes warning:
converter-example.c: In function ‘main’:
converter-example.c:400:8: warning: implicit declaration of function ‘isatty’ [-Wimplicit-function-declaration]
     if(isatty(1)) {
        ^

Fixes check-src/check-135.-gen-OER.c and check-src/check64-136.-gen-OER.c

Free the internal buffers

This fix the following ubsan error
check-62.c:36:2: runtime error: null pointer passed as argument 2, which is declared to never be null

The asn_set_add calls realloc in some of the cases and the struct cannot
be freed correctly when the sub-structs are allocated on the stack