startup: check again for a Linux console after reading all files

When there is a dash among the files on the command line, nano will read
data from standard input, which means that the latter is not connected to
a terminal and thus cannot be recognized as a Linux VT until nano has
finished reading the input and has reconnected the input source to the
terminal.

The first probe for a Linux VT is kept in place for now, so that nano
can stop when there are errors in an rcfile while running on a VT.
(This stopping will not work when data is read from standard input,
of course, but that is a smaller fish.)

This fixes https://savannah.gnu.org/bugs/?55912.
Reported-by: Enrico Mioso <mrkiko.rs@gmail.com>

Bug existed since the recognition of modified cursor keys on a Linux
console was introduced, in version 2.6.3, commit 290d278f.

src/nano.c

@@ -2685,6 +2685,11 @@ int main(int argc, char **argv)
 	}
 #endif
 
+#ifdef __linux__
+	/* Check again whether we're running on a Linux console. */
+	on_a_vt = (ioctl(0, VT_GETSTATE, &dummy) == 0);
+#endif
+
 #ifdef DEBUG
 	fprintf(stderr, "Main: show title bar, and enter main loop\n");
 #endif