Removed check for source normals, since only the target cloud is required to have normals.
Fixed MSVC linker crash.

* Linking pcl_features hit 4GB memory limit in release mode. Disabled whole program optimization and link-time code generation as a workaround.
Merge pull request #345 from jakobwilm/transformation_estimation_fix

Removed check for source normals
Merge pull request #350 from kwaegel/msvc_linker_fix

Fixed MSVC linker crash.