plugins add win modifiers before libwebsockets.h for dll export flag

CMakeLists.txt

plugin-standalone/protocol_example_standalone.c

plugins/protocol_client_loopback_test.c

plugins/protocol_dumb_increment.c

plugins/protocol_lws_mirror.c

plugins/protocol_lws_server_status.c

plugins/protocol_lws_status.c

plugins/protocol_post_demo.c