For all except "STATUS" message() will write to stderr, and this also includes
case when you does not have <mode> at all. Plus for every message in stderr
powershell generates exception and make appveyor fails.
Fixes: https://ci.appveyor.com/project/azat/libevent/build/2.1.5.85/job/i10k7m0t80330mtr
event_extra
CACHE STRING "Libevent libraries")
-message("")
-message(" ---( Libevent " ${EVENT_VERSION} " )---")
-message("")
+message(STATUS "")
+message(STATUS " ---( Libevent " ${EVENT_VERSION} " )---")
+message(STATUS "")
message(STATUS "Available event backends: ${BACKENDS}")
message(STATUS "CMAKE_BINARY_DIR: " ${CMAKE_BINARY_DIR})
message(STATUS "CMAKE_CURRENT_BINARY_DIR: " ${CMAKE_CURRENT_BINARY_DIR})
message(STATUS "CMAKE_C_COMPILER: " ${CMAKE_C_COMPILER} )
message(STATUS "CMAKE_AR: " ${CMAKE_AR} )
message(STATUS "CMAKE_RANLIB: " ${CMAKE_RANLIB} )
-message("")
+message(STATUS "")