ShadingSystem attributes: add 'compile_report' to control whether or not
info messages sent for each shader optimized & compiled;
remove unused 'rebind' attribute; add better attribute docs to header.
Speedup implementation of exp for some broken Linux platforms
testsuite/blendmath: Check derivs of mix test
When attribute 'countlayerexecs' is on, count total layers executed.
Make mix a built-in, rather than defined in stdosl.h.

Constant fold like crazy (improves some production frames by 3-4%).

Also tried new secret sauce: when the mix inputs are parameters
connected to earlier layers, add conditional evaluation in order to
reduce triggering earlier layers from running when only one input is
really needed. (This can be selectively disabled by a new "opt_mix"
attribute.)  But, alas, this makes only a very tiny additional speedup
in my production benchmarks (measurable, but insignificant).

Lots of miscellaneous infrastructure added and some refactoring, to make
all this easier.  Should be helpful for other things as well.
Fix constant that was making errors on 32 bit platforms
Fix string formatting that was generating warnings on 32 bit platforms.
CHANGES update
pointcloud function safety when passed empty filename
Bug fix: pointcloud_get should not fail when count=0.
When user asks to retrieve 0 points, success is guaranteed!
Fix wave preprocessor build error with OIIO::Strutil::format (with gcc 4.7.2).
Fix crash with cpp preprocessor when #include fails or no shader function is
defined. In case #include failed it was not properly stopping. Now it checks
the pclose exit status, but after this it could still crash with no shader
function defined, so a check was added for that as well.
Fixes for static linking of liboslcomp:
* Conflicting function names in oslgram.y when linking both oslexec and oslcomp
  libraries.
* Static initialization order issue with OSL globals TypeSpecs that depend on
  OIIO, simple solution is to move the globals array into the init_globals
  function.

(fix by Lukas Tönne)
Add parameter to OSLCompiler::compile to specify the path to the stdosl.h file,
instead of the default location of $executable/../shaders/stdosl.h.
Add ShadingSystem.LoadMemoryShader function to load a shader with OSO data
directly from a memory buffer, rather than from a file.
Rename LoadMemoryShader to LoadMemoryCompiledShader
Made README to proper markdown
Additional fixes needed to properly install the renamed README.md
Eliminate circumstances leading to an assertion, wasn't really a bug

ShaderInstance::param_range should return [begin,end), but the symbol()
function it used for the begin and end pointers would assert if past the
last symbol, which of course the "non-inclusive" end needed to be.  Ugh.
Addressed compilation error caused by using the -Werror option on g++ 4.7.2.
(This is the default option given in the ./src/CMakeLists.txt file)

Return boolean variable "ok" instead of hardcoded "false" in USE_PARTIO section of the
code.
(This section of the code is only compiled if the partio library is installed)