Made the generated file templates' naming more consistent.

The general convention is <output file name> + ".in".

cmake/OpenCVGenHeaders.cmake

 # platform-specific config file
-configure_file("${OpenCV_SOURCE_DIR}/cmake/templates/cvconfig.h.cmake" "${OPENCV_CONFIG_FILE_INCLUDE_DIR}/cvconfig.h")
+configure_file("${OpenCV_SOURCE_DIR}/cmake/templates/cvconfig.h.in" "${OPENCV_CONFIG_FILE_INCLUDE_DIR}/cvconfig.h")
 
 # ----------------------------------------------------------------------------
 #  opencv_modules.hpp based on actual modules list

cmake/OpenCVGenPkgconfig.cmake

@@ -76,7 +76,9 @@ if(INSTALL_TO_MANGLED_PATHS)
 else()
   set(OPENCV_PC_FILE_NAME opencv.pc)
 endif()
-configure_file("${OpenCV_SOURCE_DIR}/cmake/templates/opencv-XXX.pc.cmake.in" "${CMAKE_BINARY_DIR}/unix-install/${OPENCV_PC_FILE_NAME}" @ONLY IMMEDIATE)
+configure_file("${OpenCV_SOURCE_DIR}/cmake/templates/opencv-XXX.pc.in"
+               "${CMAKE_BINARY_DIR}/unix-install/${OPENCV_PC_FILE_NAME}"
+               @ONLY IMMEDIATE)
 
 if(UNIX AND NOT ANDROID)
   install(FILES ${CMAKE_BINARY_DIR}/unix-install/${OPENCV_PC_FILE_NAME} DESTINATION ${OPENCV_LIB_INSTALL_PATH}/pkgconfig)