Rename IPv4 only functions to include _ipv4_

Currently:

  • IPv6-only functions are named *_ipv6_*, for example set_ipv6_exclude_route.
  • IPv4-only functions lack *_ipv4_*, for example set_ipv6_default_route.
  • Functions operating on both address families also lack *_ipv4_*, for example set_vpngateway_route.

I feel renaming IPv4-only functions to include _ipv4_ would clarify the code.

Edited by Dimitri Papadopoulos Orfanos