add visual studio project to compile as a .dll
add defines to allow for .dll compilation and usage
Change the dll name from SpoutSDK to Spout
rename the DLLEXP to SPOUT_DLLEXP to avoid collisions
add some const correctness to these files

makes it easier to work with when coming from external code that is const correct.
add _MSC_VER define
add README file for the .dll project
Merge pull request #1 from mbechard/master

a MSVC2010 project to create .dll, some related code changes. Also some const correctness