Remove $(TIRPCINC) from all Makefile.am files - it no longer exists

Also, restructure some of the dependencies in the lib/tt binaries.  We
will link with libtt (which will include libtirpc as a dependency),
and XTOOLLIB - all the right X11 stuff without needing to add it to
every OS.  Removed several uneeded OS specializations ("if LINUX",
etc) as a result.

cde/programs/dtwm/Makefile.am

@@ -8,8 +8,7 @@ CLEANFILES = sys.dtwmrc Dtwm.defs
 
 AM_CPPFLAGS = -DLARGECURSORS -DR2_COMPAT -DOPAQUE -DSHAPE -DUNMAP_ON_RESTART \
 	      -DBATCH_DRAG_REQUESTS -DCDE_INSTALLATION_TOP=\"${prefix}\" \
-	      -DCDE_CONFIGURATION_TOP=\"$(CDE_CONFIGURATION_TOP)\" \
-	      $(TIRPCINC)
+	      -DCDE_CONFIGURATION_TOP=\"$(CDE_CONFIGURATION_TOP)\"
 
 dtwm_LDADD = @DTCLIENTLIBS@ $(TIRPCLIB) -lXm -lXext $(XTOOLLIB)
 dtfplist_LDADD = @DTCLIENTLIBS@ $(TIRPCLIB) -lXm -lXext $(XTOOLLIB)