Cherry pick trunk@13760 to remove boost::system
per https://marc.info/?l=openbsd-ports&m=177038373917003&w=2

Index: src/plugins/contrib/NassiShneiderman/Makefile.am
--- src/plugins/contrib/NassiShneiderman/Makefile.am.orig
+++ src/plugins/contrib/NassiShneiderman/Makefile.am
@@ -1,8 +1,7 @@
 AM_CPPFLAGS = $(WX_CXXFLAGS) \
 		-I$(top_srcdir)/src/include \
 		-I$(top_srcdir)/src/sdk/wxscintilla/include \
-		$(BOOST_CPPFLAGS) \
-		-DBOOST_SYSTEM_NO_DEPRECATED
+		$(BOOST_CPPFLAGS)
 
 pluginlibdir = $(pkglibdir)/plugins
 
