Adds curl support to main core

Curl was used only by mlogc, as we want to expand ModSecurity to load
external rules/resources it is now a dependency of the core as well.
Adds support to load remote resources to pmFromFile and ipMatchFromFile

Initially those directives were only able to load content from a
local file. This commit extends this functionality allowing the user to
provide an HTTP URI that can be downloaded and loaded by ModSecurity.
Initially the download is associated with a server restart. For next
versions we expect to load such resources as it become outdated (Without
need to resetart the server).
Initial support to load rules from a remote server

New directive `SecRemoteRules' was added. It allows the user to load a
set of rules from a given HTTP server.