Bug fix in wrap_periodic_sharedborder (used by environment call with exr maps)
The math here made an assumption that the amount of periodic wrapping could
be no more than 1 cycle.  But it could!  If using a bicubic lookup (needs 4
samples) at a MIP level with resolution <= 2 (very blurry), you could
mis-calculate the wrap and end up with a coordinate out of the range of
valid pixels.
Fix resolution formatting bug -- mixed up order of format arguments.
Use fingerprint instead of filename to delete fingerprint in invalidate
iv: fix bug where 'reload' would lose track of the image.
(This bug was introduced recently by the ImageBuf PIMPL overhaul.)
Fix strutil.cpp for WIN32

Prevent collision with max() macro
InterlockedExchangeAdd64 implementation for XP

Prevent OpenImageIO.dll to fail when dynamically loaded on XP.
Compilation for the XP target must be explicitely selected.
Export symbols for testtex
Fix command help for oiiotool
ImageBufAlgo::paste copies a region from one ImageBuf to another
oiiotool --fit : resize to fit a particular resolution
Extend functionality of ImageBufAlgo::channels with values and channel names.

Add a new IBA::channels() variety that lets you optionally take a list
of channel literal values (instead of using 0 for dst channels not
corresponding to src channels) and new channel names (so you can rename
channels in addition to shuffling them.

The old call is considered deprecated, but kept for link compatibility (and
merely calls the newer, more general, version).
Extend functionality of oiiotool --ch to name new channels.

Previously, the 'oiiocool --ch' let you specify some shuffled channels
as literal values like this: oiiotool --ch R,G,B,A,=1.0
In this example, it would add a 5th channel, set to 1.0 everywhere.
However, the extra channel will just be named "channel 4", because it
has no idea what it actually means.

In this patch, we extend the syntax to allow 'name=value' liks this:
oiiotool --ch R,G,B,A,Z=1.0
This lets you name the literal channels that you add, and further
(by virtue of newly added functionality of IBA::channels), it will
recognize "Z" as a special name and also mark the spec.z_channel to
be that channel in the new image.