CMake: consistently use *_PRIVATE_HEADERS as a variable name.

src/Magnum/Math/CMakeLists.txt

@@ -72,13 +72,13 @@ if(MAGNUM_BUILD_DEPRECATED)
     list(APPEND MagnumMath_HEADERS BoolVector.h)
 endif()
 
-set(MagnumMath_INTERNAL_HEADERS
+set(MagnumMath_PRIVATE_HEADERS
     Implementation/halfTables.hpp)
 
 # Force IDEs to display all header files in project view
 add_custom_target(MagnumMath SOURCES
     ${MagnumMath_HEADERS}
-    ${MagnumMath_INTERNAL_HEADERS})
+    ${MagnumMath_PRIVATE_HEADERS})
 
 install(FILES ${MagnumMath_HEADERS} DESTINATION ${MAGNUM_INCLUDE_INSTALL_DIR}/Math)
 

src/Magnum/MeshTools/CMakeLists.txt

@@ -70,7 +70,7 @@ set(MagnumMeshTools_HEADERS
 
     visibility.h)
 
-set(MagnumMeshTools_INTERNAL_HEADERS
+set(MagnumMeshTools_PRIVATE_HEADERS
     Implementation/remapAttributeData.h
     Implementation/Tipsify.h)
 
@@ -107,7 +107,7 @@ endif()
 add_library(MagnumMeshToolsObjects OBJECT
     ${MagnumMeshTools_SRCS}
     ${MagnumMeshTools_HEADERS}
-    ${MagnumMeshTools_INTERNAL_HEADERS})
+    ${MagnumMeshTools_PRIVATE_HEADERS})
 target_include_directories(MagnumMeshToolsObjects PUBLIC $<TARGET_PROPERTY:Magnum,INTERFACE_INCLUDE_DIRECTORIES>)
 if(NOT MAGNUM_BUILD_STATIC)
     target_compile_definitions(MagnumMeshToolsObjects PRIVATE "MagnumMeshToolsObjects_EXPORTS")