add cmake uninstall functionality

- add uninstall functionality
  * see https://cmake.org/Wiki/CMake_FAQ#Can_I_do_.22make_uninstall.22_with_CMake.3F

CMakeLists.txt

@@ -224,3 +224,11 @@ if(NOT MSVC)
 	add_subdirectory(man)
 	add_subdirectory(tests)
 endif()
+
+configure_file(
+	"${CMAKE_CURRENT_SOURCE_DIR}/cmake_uninstall.cmake.in"
+	"${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake"
+	IMMEDIATE @ONLY)
+
+add_custom_target(uninstall
+	COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)

Makefile.am

@@ -5,7 +5,7 @@ pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = libcrypto.pc libssl.pc libtls.pc openssl.pc
 
 EXTRA_DIST = README.md README.windows VERSION config scripts
-EXTRA_DIST += CMakeLists.txt
+EXTRA_DIST += CMakeLists.txt cmake_uninstall.cmake.in
 
 .PHONY: install_sw
 install_sw: install

cmake_uninstall.cmake.in

@@ -0,0 +1,21 @@
+if(NOT EXISTS "@CMAKE_CURRENT_BINARY_DIR@/install_manifest.txt")
+	message(FATAL_ERROR "Cannot find install manifest: @CMAKE_CURRENT_BINARY_DIR@/install_manifest.txt")
+endif(NOT EXISTS "@CMAKE_CURRENT_BINARY_DIR@/install_manifest.txt")
+
+file(READ "@CMAKE_CURRENT_BINARY_DIR@/install_manifest.txt" files)
+string(REGEX REPLACE "\n" ";" files "${files}")
+foreach(file ${files})
+	message(STATUS "Uninstalling $ENV{DESTDIR}${file}")
+	if(IS_SYMLINK "$ENV{DESTDIR}${file}" OR EXISTS "$ENV{DESTDIR}${file}")
+		exec_program(
+			"@CMAKE_COMMAND@" ARGS "-E remove \"$ENV{DESTDIR}${file}\""
+			OUTPUT_VARIABLE rm_out
+			RETURN_VALUE rm_retval
+			)
+		if(NOT "${rm_retval}" STREQUAL 0)
+			message(FATAL_ERROR "Problem when removing $ENV{DESTDIR}${file}")
+		endif(NOT "${rm_retval}" STREQUAL 0)
+	else(IS_SYMLINK "$ENV{DESTDIR}${file}" OR EXISTS "$ENV{DESTDIR}${file}")
+		message(STATUS "File $ENV{DESTDIR}${file} does not exist.")
+	endif(IS_SYMLINK "$ENV{DESTDIR}${file}" OR EXISTS "$ENV{DESTDIR}${file}")
+endforeach(file)