add CMake find function for libwebsockets

Signed-off-by: Jiri Hnidek <jiri.hnidek@tul.cz>

scripts/FindLibWebSockets.cmake

+# This module tries to find libWebsockets library and include files
+#
+# LIBWEBSOCKETS_INCLUDE_DIR, path where to find libwebsockets.h
+# LIBWEBSOCKETS_LIBRARY_DIR, path where to find libwebsockets.so
+# LIBWEBSOCKETS_LIBRARIES, the library to link against
+# LIBWEBSOCKETS_FOUND, If false, do not try to use libWebSockets
+#
+# This currently works probably only for Linux
+
+FIND_PATH ( LIBWEBSOCKETS_INCLUDE_DIR libwebsockets.h
+    /usr/local/include
+    /usr/include
+)
+
+FIND_LIBRARY ( LIBWEBSOCKETS_LIBRARIES websockets
+    /usr/local/lib
+    /usr/lib
+)
+
+GET_FILENAME_COMPONENT( LIBWEBSOCKETS_LIBRARY_DIR ${LIBWEBSOCKETS_LIBRARIES} PATH )
+
+SET ( LIBWEBSOCKETS_FOUND "NO" )
+IF ( LIBWEBSOCKETS_INCLUDE_DIR )
+    IF ( LIBWEBSOCKETS_LIBRARIES )
+        SET ( LIBWEBSOCKETS_FOUND "YES" )
+    ENDIF ( LIBWEBSOCKETS_LIBRARIES )
+ENDIF ( LIBWEBSOCKETS_INCLUDE_DIR )
+
+MARK_AS_ADVANCED(
+    LIBWEBSOCKETS_LIBRARY_DIR
+    LIBWEBSOCKETS_INCLUDE_DIR
+    LIBWEBSOCKETS_LIBRARIES
+)