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/dtmail/dtmailpr/Makefile.am

@@ -3,7 +3,7 @@ MAINTAINERCLEANFILES = Makefile.in
 bin_PROGRAMS = dtmailpr
 
 dtmailpr_CXXFLAGS = -I../include -I../../dtcompat -I../../../. \
-		    -I$(srcdir)/lib $(TIRPCINC)
+		    -I$(srcdir)/lib
 
 dtmailpr_LDADD = ../libDtMail/libDtMail.a @DTCLIENTLIBS@ \
 		 -lXm @LIBXIN@ -lXinerama $(XTOOLLIB) ${X_LIBS} $(TIRPCLIB)