Ported Autodesk optimisations
Merge branch 'develop' into iif-weta
Support converting scanline EXRs to multipart files using exrmultipart
Ported optimization test to IlmImfTest
optimization test uses namespace macro properly
Syncing over with ILM internal updates.
Fixed misinterpretation of dtex samples in deepopacity case, updated README, comments, and ChangeLog to reflect fix.
Merge branch 'develop' into iif-weta
Folding in the changes for switching on the availability of the SSE2 instruction set.

From Brendan Bolles (fnordware)

There are many options for Windows SSE2 flags, most of which are not
optimal. We'd rather have a false positive (possibly resulting in a
compiler error that we could then expore further) than a false negative.

_M_IX86_FP == 2 will tell you that the compiler flags are set to SSE2,
but they are often not set and SSE2 would still build properly if we
allow it.

_M_IX86 || _M_X64 would assume that all Intel CPUs had SSE2, but would
incorrectly include the headers on old versions of Visual Studio.

_MSC_VER >= 1300 seems to be the best test. This corresponds to Visual
Studio .NET 2002, the first version that had SSE2.

_M_CEE_PURE also must be off. Google it.
Added missing file
Added missing file.
Added isOptimizationEnabled() and test
fixed documentation typos, readPixelSampeCounts, documented rawPixelData deepscanline calls
Added existing stream support to MultiPartOutputFile - under test
Fixed multipart file output bug caused by refactor
formatting error in exception message
Refactor for gcc-4.0: nested classes do not inherit 'friend' status in earlier standard

Input/OutputPartData now structs not classes
templated getInputPart and getOutputPart moved to MultiPartInputFile and MultiPartOutputFile rather than their respective ::Data members
create*Part functions in MultiPartInputFile and MultiPartOutputFile removed: internally using getInput/OutputPart<> instead
Extraneous displayWindow call removed from writeHeadersToFile()
Switch #include <Imf...> to #include "Imf..." in most .cpp files
TileOffsets::isValidTile made public not private
TileOffsets::getOffsets() made const public not non-const private
Reduce compiler warnings

Changing ints to size_t types where valid
Initialise variables in makeTiled.cpp
avoid "unhandled NUM_PIXELTTYPES" with default

Use defines for "deepscanline" etc in exrmultipart
test and fixes to support files with unknown part types
future proofing: test for version!=1 deep images