Don't include pcap headers if you don't have pcap.

Don't try to compile code that uses pcap if you don't have it.

Change-Id: Ifa98b4ff47783f5347cb6e1129bbf4e5cac35aab
Reviewed-on: https://code.wireshark.org/review/21611
Reviewed-by: Guy Harris <guy@alum.mit.edu>

ui/qt/compiled_filter_output.cpp

@@ -19,6 +19,9 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "config.h"
+
+#ifdef HAVE_LIBPCAP
 
 #include <ui_compiled_filter_output.h>
 #include "compiled_filter_output.h"
@@ -124,6 +127,8 @@ void CompiledFilterOutput::copyFilterText()
     wsApp->clipboard()->setText(ui->filterList->toPlainText());
 }
 
+#endif /* HAVE_LIBPCAP */
+
 //
 // Editor modelines  -  http://www.wireshark.org/tools/modelines.html
 //