export DLLs functions for MSVC with CMake

- Add 3 DEF files to export functions from Windows DLLs
  - Add gettimeofday to crypto/crypto.def (*1)
  - Remove gai_strerrorA from tls/tls.def (*1)
- Fix CMakeLists.txt to use DEF files as PRIVATE
- Change DLL import library file name since it duplicates with static library
- Ignore compiler warning C4267, and Edit CMAKE_C_FLAGS not to overwrite it (*1)
- Add USE_SHARED option to build openssl.exe with shared libraries (*1)

  (*1) recommended by @mcnameej

ssl/CMakeLists.txt

@@ -53,11 +53,14 @@ if (BUILD_SHARED)
 	add_library(ssl STATIC $<TARGET_OBJECTS:ssl-objects>)
 	add_library(ssl-shared SHARED $<TARGET_OBJECTS:ssl-objects>)
 	if (WIN32)
+		target_sources(ssl-shared PRIVATE
+			${CMAKE_CURRENT_SOURCE_DIR}/ssl.def)
 		target_link_libraries(ssl-shared crypto-shared Ws2_32.lib)
 		set(SSL_POSTFIX -${SSL_MAJOR_VERSION})
 	endif()
 	set_target_properties(ssl-shared PROPERTIES
-		OUTPUT_NAME ssl${SSL_POSTFIX} ARCHIVE_OUTPUT_NAME ssl)
+		OUTPUT_NAME ssl${SSL_POSTFIX}
+		ARCHIVE_OUTPUT_NAME ssl${SSL_POSTFIX})
 	set_target_properties(ssl-shared PROPERTIES VERSION ${SSL_VERSION}
 		SOVERSION ${SSL_MAJOR_VERSION})
 	install(TARGETS ssl ssl-shared DESTINATION lib)