This reverts commit ed81dd30.
The state of digit validation is highly controversial.  I give
up.  :)

While this is a neat milestone, it becomes apparent how convuluted
the code path and interface info polling is.  Looking at it, the
whole interface layer can probably make performance jumps to at least
twice the read or reconfigure speed...

enable the opnsense test ruleset and try to download the eicar virus:

http://www.eicar.org/download/eicar.com.txt

it should block (over http)

closes https://github.com/opnsense/core/issues/884

Only one function left.  :)

BTW: 5000 commits on master branch, yay, party!

Needs a bit of observation, but as far as I can see the only difference
is that is_numeric() will also take int values and return true for them,
ctype_digit() will only return true for string values that have digits.

Taken from: http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml