[CMake] put python header in include

Otherwise, this header is installed if BUILD_PYTHON_INTERFACE, and not
if INSTALL_PYTHON_INTERFACE_ONLY.

But if we want to be able to have binary packages for:
- the main curve package
- its bindings for python 2
- its bindings for python 3

this header will be installed in the 2 last cases, which will conflict.

In short: if we set INSTALL_PYTHON_INTERFACE_ONLY, there should be only
stuff installed in PYTHON_SITELIB.

include/curves/CMakeLists.txt

@@ -25,4 +25,5 @@ INSTALL(FILES
 
 ADD_SUBDIRECTORY(helpers)
 ADD_SUBDIRECTORY(optimization)
+ADD_SUBDIRECTORY(python)
 ADD_SUBDIRECTORY(serialization)

include/curves/python/CMakeLists.txt

+SET(${PROJECT_NAME}_PYTHON_HEADERS
+  python_definitions.h
+  )
+
+INSTALL(FILES
+  ${${PROJECT_NAME}_PYTHON_HEADERS}
+  DESTINATION include/${PROJECT_NAME}/python
+  )

python/curves/CMakeLists.txt

@@ -8,15 +8,6 @@ SET(${PY_NAME}_BINDINGS_SOURCES
   namespace.h
   )
 
-SET(${PROJECT_NAME}_PYTHON_HEADERS
-  python_definitions.h
-  )
-
-INSTALL(FILES
-  ${${PROJECT_NAME}_PYTHON_HEADERS}
-  DESTINATION include/${PROJECT_NAME}/python
-  )
-
 ADD_LIBRARY(${PY_NAME} SHARED ${${PY_NAME}_BINDINGS_SOURCES})
 SET_TARGET_PROPERTIES(${PY_NAME} PROPERTIES PREFIX "")
 TARGET_COMPILE_OPTIONS(${PY_NAME} PRIVATE "-Wno-conversion")

python/curves/python_variables.cpp

 #include "python_variables.h"
-#include "python_definitions.h"
+#include "curves/python/python_definitions.h"
 
 #include <Eigen/Core>
 

python/curves/python_variables.h

@@ -10,7 +10,7 @@
 #include "curves/piecewise_curve.h"
 #include "curves/so3_linear.h"
 #include "curves/se3_curve.h"
-#include "python_definitions.h"
+#include "curves/python/python_definitions.h"
 #include <eigenpy/memory.hpp>
 #include <eigenpy/eigenpy.hpp>
 #include <eigenpy/geometry.hpp>