Fix is_ipv4_netmask_pair
Fix is_ipv4_netmask_pair

The limit parameter of `split()` doesn't work as expected, it actually
limits the number of results (i.e. the regex is matched limit - 1 times).

This meant `is_ipv4_netmask_pair` never matched anything.

Doh.

alvarosimon/template-library-core,quattor/template-library-core,jouvin/template-library-core,jrha/template-library-core,apdibbo/template-library-core