Single compilation units

Even before reading 1, we noticed a great speed up in compile time for all PCL libraries if instead of compiling N object files and linking them together, we compile only one, and include all the sources of the N files in this main source. If you peek at an older version of PCL, you might notice things along the lines of:

1 // Include the implementations instead of compiling them separately to speed up compile time
2 #include "extract_indices.cpp"
3 #include "passthrough.cpp"
4 #include "project_inliers.cpp"
5 #include "statistical_outlier_removal.cpp"
6 #include "voxel_grid.cpp"

and in CMakeLists.txt:

1 rosbuild_add_library (pcl_ros_filters
2                       src/pcl_ros/filters/filter.cpp
3                       # Compilation is much faster if we include all the following CPP files in filters.cpp
4                       #src/pcl_ros/filters/passthrough.cpp
5                       #src/pcl_ros/filters/project_inliers.cpp
6                       #src/pcl_ros/filters/extract_indices.cpp
7                       #src/pcl_ros/filters/statistical_outlier_removal.cpp
8                       #src/pcl_ros/filters/voxel_grid.cpp
9                      )

For more information on how/why this works, see 1.