Fix no-stdio build

Much related/similar work also done by
Ivan Nestlerode <ivan.nestlerode@sonos.com>

   +Replace FILE BIO's with dummy ops that fail.
   +Include <stdio.h> for sscanf() even with no-stdio (since the declaration
    is there). We rely on sscanf() to parse the OPENSSL_ia32cap environment
    variable, since it can be larger than a 'long'. And we don't rely on the
    availability of strtoull().
   +Remove OPENSSL_stderr(); not used.
   +Make OPENSSL_showfatal() do nothing (currently without stdio there's
    nothing we can do).
   +Remove file-based functionality from ssl/. The function
    prototypes were already gone, but not the functions themselves.
   +Remove unviable conf functionality via SYS_UEFI
   +Add fallback definition of BUFSIZ.
   +Remove functions taking FILE * from header files.
   +Add missing DECLARE_PEM_write_fp_const
   +Disable X509_LOOKUP_hash_dir(). X509_LOOKUP_file() was already compiled out,
    so remove its prototype.
   +Use OPENSSL_showfatal() in CRYPTO_destro...