ports/*/jpeg "Thanks a lot guys"

[Buganini]

The meaning of NODE_VERSION and the flag is to describe dependencies more
detailed,
to make it possible to do automated upgrade, instead of bump PORTREVISION by
man.

An important thing, NODE_VERSION and the flag could be backward compatible,
for port/package don't have NODE_VERSION, it's just 0.
the flag could be just a '!' prefix, for example:
!fltk-threads>=1.1.9:${PORTSDIR}/x11-toolkits/fltk-threads
QT_COMPONENTS=  gui imageformats_run moc_build !qmake_build !uic_build
without the flag, everything is just like how it is now.

this should be enough for cases like this jpeg case.
For more detail, if we only save NODE_VERSION of port itself in +CONTENTS
upgrade MUST be transactional, but for portupgrade and portmaster, exit in
half way is usual,
so I think to save NODE_VERSION of each dependencies is also necessary,
or even make it part of version string, but this may be confused for
somebody I think.

For the upgrade of perl, now we use port* -o to replace, then -r or -fr to
rebulid required-by
If we have
NODE_VERSION=5.8.0 in lang/perl5.8
NODE_VERSION=5.10.0 in lang/perl5.10
then when we port{upgrade,master} -o lang/perl5.10 perl5.8
we dont have to rebuild required-by manually anymore.

Furthermore, a unified target post-upgrade: is good, some ports has already
have this,
for example, upgrade-site-packages in lang/python

--Buganini