Rename ipifyipv{4,6} to ipify-ipv{4,6}

The added dash makes it easier to read.

ChangeLog.md

@@ -21,7 +21,7 @@ repository history](https://github.com/ddclient/ddclient/commits/master).
   * New `ssl_ca_dir` and `ssl_ca_file` options to specify the location of CA
     certificates.
   * New built-in IP discovery service shorthands:
-      - `ipifyipv4` and `ipifyipv6` from https://www.ipify.org
+      - `ipify-ipv4` and `ipify-ipv6` from https://www.ipify.org
       - `myonlineportal` from https://myonlineportal.net
   * New built-in shorthands for obtaining the IP address from the following
     devices ([thanks to Geoff Simmons](https://bugs.debian.org/589980)):

ddclient.in

@@ -97,8 +97,8 @@ sub T_POSTS  { 'postscript' }
 ## strategies for obtaining an ip address.
 my %builtinweb = (
     'dyndns' => {'url' => 'http://checkip.dyndns.org/', 'skip' => 'Current IP Address:'},
-    'ipifyipv4' => {'url' => 'https://api.ipify.org/'},
-    'ipifyipv6' => {'url' => 'https://api6.ipify.org/'},
+    'ipify-ipv4' => {'url' => 'https://api.ipify.org/'},
+    'ipify-ipv6' => {'url' => 'https://api6.ipify.org/'},
     'loopia' => {'url' => 'http://dns.loopia.se/checkip/checkip.php', 'skip' => 'Current IP Address:'},
     'myonlineportal' => {'url' => 'https://myonlineportal.net/checkip'},
 );