bsdtar: Fix error handling around strtol() usages (#2110)

bsdtar: Fix error handling around strtol() usages (#2110)

The code here had a couple of bad code patterns that seem to have been
copied throughout:
* Checking errno after strtol() -- Standard C doesn't seem to actually
require this, so we shouldn't rely on it
* Casting the result of strtol() directly to `int`. This loses
information prematurely.

Instead, I've added `l` as a temporary of type `long`, use that to hold
the result of `strtol()` until it can be checked. I've also removed the
`errno` tests in favor of checking the end pointer value.

The limit for --strip-components has been raised to 100 000.