Fix 4-byte-ASN-related on JunOS

re2dfa & rpsl had a couple of hardcoded assumptions of 2-byte ASNs,
including a hard limit of 65535. Fix all of those occurences.

This is a rebase of a 2013 patch by Daryl Collins, which is based on a
2010 patch by Timo Koehler, which is in turn based on a 2008 patch by
yours truly.
Do not use non-standard strcasestr()

It fails on Solaris. Since we're only interested in the string "AS",
replace it in-place with tolower().
Do not use -V on RIPE/Bird WHOIS queries

irtoolset currently sends -V <ProjectVersion> for all of its WHOIS
queries.

RIPE's Database Query Reference Manual, section "Access Control for
Queries" mentions that this is used by proxies to indicate the client's
IP address in the syntax
    -V <version>,<ipv4-address>
which is obviously not something that irrtoolset does or needs.

The help output in RIPE's own WHOIS server, however, mentions:
    -V<client-tag>   Sends information about the client to the server.
which is probably the reason for this misconception.

(in HTTP terms, that would be a Via vs. User-Agent header)

The WHOIS server's source indicates that the former is the proper
meaning of the flag and even irrtoolset clients that try to pass that
without being explicitelly marked as trusted proxies.

Hence, stop sending the flag altogether.
Fix rpslparse()'s prototype when using a newer toolchain

Compilation with a fairly new (Debian jessie) toolchain fails with:

../.libs/libirrtoolset.a(object.o): In function `Object::parse()':
/root/paravoid/irrtoolset/irrtoolset-5.0.1/src/rpsl/object.cc:131:
undefined reference to `rpslparse(void*)'

Fix this by adjusting for the new prototype, which doesn't need any
arguments.