minor beautifications

corresponds to Perforce change 6075.
fixed two yet unreported bugs:
- Iridescence did not properly honor full area diffuse lighting.
- Subsurface scattering did not play nice with non-default brilliance values.

corresponds to Perforce change 6076.
require boost >= 1.38

corresponds to Perforce change 6077.
minor improvements in SSLT relating to the storage of precomputed values

corresponds to Perforce change 6078.
more sophisticated way of pulling in the libtiff headers in povray.cpp without breaking the Windows build

corresponds to Perforce change 6079.
minor change in how zlib is included in povmscpp.cpp

corresponds to Perforce change 6080.
minor robustness improvement in IFF image reading code

corresponds to Perforce change 6081.
atmospheric fog, rainbows and sky spheres now use C++ style memory allocation instead of POV_MALLOC

corresponds to Perforce change 6082.
eliminated a host of C-style pointer casts, mostly by replacing with C++-style casts

corresponds to Perforce changes 6083, 6084, 6085.
hotfix for residual issues with FS#270; the artifacts still observed with radiosity abort-continue will now only show in the preview, but not in the generated image file.

corresponds to Perforce change 6086.
VS2010 kept reporting GUI project to be out of date even if it wasn't; fixed.

corresponds to Perforce change 6088.
preliminary workaround for FS#313 (radiosity.cpp pov::RadiosityFunction::BeforeTile assertion failed)

corresponds to Perforce change 6092.
various changes related to color computations.

corresponds to Perforce changes 6089, 6090, 6095, 6096, 6097, 6113.
eliminating some redundant computations in SSLT code

corresponds to Perforce changes 6109, 6110.
fix for build error introduced with latest change (forgot to commit types.h)
Merge branch 'hotfix'
added header files to hold Unix flavor-specific config settings; also thrown out the unused fseek64 macro from both Unix and Windows syspovconfig.h; should fix GitHub issue #9.

corresponds to Perforce changes 6129, 6131, 6133.
eliminate uint type from platform-independent code; fixes GitHub issue #10

corresponds to Perforce change 6130.
now using std::tr1 smart pointers if available, or boost's implementation otherwise; we're using <boost/tr1/memory.hpp> to pull in either. Should fix GitHub issue #8.

corresponds to Perforce change 6132.
fix GitHub issues #5 and #6.

corresponds to Perforce changes 6135, 6136.