termcap.c: fix: add missing _F_NOENT check..

termcap.c: fix: add missing _F_NOENT check..

After a hard time on Solaris and FreeBSD (and that even calls
itself "xterm"!) terminal i finally found the cause why the cursor
doesn't move after mle-go-home: the terminal fails to provide the
hpa/ch command!

But instead of choosing our alternative builtin approach in this
case, we just kept it hanging around in _F_NOENT state, because
a_termcap_init_altern() only checked for "any flags at all" after
first zeroing out those fields which the user explicitly disabled
via an empty entry in *termcap*.

So overwrite those entries which have _F_NOENT set due to a failed
terminal library lookup in addition.

While here: provide some -d/-vv logging for *termcap* parsing, and
also disable those entries of *termcap* which had parse failures.