CMake: check for htobe64 in sys/endian.h as well

Closes #499

Credits and thanks go to Derek Schrock for pointing this out.

Author: bk138

CMakeLists.txt

@@ -212,6 +212,7 @@ check_function_exists(strerror        LIBVNCSERVER_HAVE_STRERROR)
 check_function_exists(strstr          LIBVNCSERVER_HAVE_STRSTR)
 
 check_symbol_exists(htobe64 "endian.h" LIBVNCSERVER_HAVE_HTOBE64)
+check_symbol_exists(htobe64 "sys/endian.h" LIBVNCSERVER_HAVE_HTOBE64)
 check_symbol_exists(OSSwapHostToBigInt64 "libkern/OSByteOrder.h" LIBVNCSERVER_HAVE_OSSWAPHOSTTOBIGINT64)
 
 if(WITH_THREADS AND Threads_FOUND)