Added SC_SCHEMA_EXPORT macro's for generated types.

Fixes MSVC linker errors in user code.
Removed duplicate definition of SchemaInit function.

SchemaInit is already declared in 'schema.h'.
Removed MSVC exclusion for SC_BUILD_STATIC_LIBS.
Split SC_ADDEXEC macro to handle static and shared libs build.
Added libraries to SC_ADDEXEC libslist parameter.

When building static libs, all dependent libraries need to be provided to liblist.
When building shared libs, this is not needed, but does not break the build.
Merge pull request #283 from stepcode/dw/msvc_linker_fixes

Msvc linker fixes + static libs