Update to 2.0001

Upstream changes:
2.0001 2021-03-29
- BUGFIX: Return a netmask length of 0 whenever parsing an invalid
  digit.
- Add "safe_new()" method to make it more clear what new2() does. Note
  that this executes the same code as new2().

2.0000 2021-03-29

- SECURITY: IPv4 addresses with leading zeros are no longer allowed.
  They will return a parse error like any invalid IP address.
- SECURITY: 10.0.0, 10.0, and 10 address portions now by default return
  a parse error.  This can be overriden by calling new() like:
    Net::Netmask->new2('10/8', shortnet => 1);    # or new()
  or
    Net::Netmask->new2('10', '8', shortnet => 1);  # or new()

  There is also a package-level variable that can change the default
  when "shortnet" isn't used passed into the constructor. Usage:
    local $Net::Netmask::SHORTNET_DEFAULT = 1;
    Net::Netmask->new('10', '8');  # or new2()

(wen)