Log message:
Attempt to bring sanity to how ABI and MACHINE_ARCH are set.

Previously there were at least 5 different ways MACHINE_ARCH could be set,
some statically and some at run time, and in many cases these settings
differed, leading to issues at pkg_add time where there was conflict
between the setting encoded into the package and that used by pkg_install.

Instead, move to a single source of truth where the correct value based on
the host and the chosen (or default) ABI is determined in the bootstrap
script.  The value can still be overridden in mk.conf if necessary, e.g.
for cross-compiling.

ABI is now set by default and if unset a default is calculated based on
MACHINE_ARCH.  This fixes some OS, e.g. Linux, where the wrong default was
previously chosen.

As a result of the refactoring there is no need for LOWER_ARCH, with
references to it replaced by MACHINE_ARCH.  SPARC_TARGET_ARCH is also
removed.

Log message:
Add SHA512 digests for distfiles for net category

Problems found with existing digests:
	Package haproxy distfile haproxy-1.5.14.tar.gz
	159f5beb8fdc6b8059ae51b53dc935d91c0fb51f [recorded]
	da39a3ee5e6b4b0d3255bfef95601890afd80709 [calculated]

Problems found locating distfiles:
	Package bsddip: missing distfile bsddip-1.02.tar.Z
	Package citrix_ica: missing distfile citrix_ica-10.6.115659/en.linuxx86.tar.gz
	Package djbdns: missing distfile djbdns-1.05-test25.diff.bz2
	Package djbdns: missing distfile djbdns-cachestats.patch
	Package djbdns: missing distfile 0002-dnscache-cache-soa-records.patch
	Package gated: missing distfile gated-3-5-11.tar.gz
	Package owncloudclient: missing distfile owncloudclient-2.0.2.tar.xz
	Package poink: missing distfile poink-1.6.tar.gz
	Package ra-rtsp-proxy: missing distfile rtspd-src-1.0.0.0.tar.gz
	Package ucspi-ssl: missing distfile ucspi-ssl-0.70-ucspitls-0.1.patch
	Package waste: missing distfile waste-source.tar.gz

Otherwise, existing SHA1 digests verified and found to be the same on
the machine holding the existing distfiles (morden).  All existing
SHA1 digests retained for now as an audit trail.

Log message:
Do not remove __attribute__, at the very least this way leads to bad
syntax in system headers on NetBSD.

Log message:
Drop superfluous PKG_DESTDIR_SUPPORT, "user-destdir" is default these days.

Log message:
updated download archives since original ftp servser seems to have become
unreachable/unavailable. Now using source archive from old Ubuntu archives
instead.

Log message:
updated download paths

Log message:
MacOS 10.6 needs -lresolv

Log message:
Traceroute-nanog is based on the Van Jacobson/BSD traceroute and has
additional features like AS lookup, TOS support, microsecond timestamps, 
path MTU discovery, parallel probing and others.