configure/Makefiles: add checks for Xmu, Xext, and Xdmcp

We also remove sun pro specific options, and do some general cleanup
as well as remove hardcoded library refs like -lXm, -lXext, etc...

cde/programs/dtudcexch/Makefile.am

@@ -6,7 +6,7 @@ dtudcexch_CFLAGS = -I$(FONTEDT_PATH1) -I$(FONTEDT_PATH1)/include \
 		   -I$(FONTEDT_PATH1)/libfal -I$(FONTEDT_PATH1)/dtgpftobdf \
 		   -DFONTC='"'$(BDFTOPCF)'"'
 
-dtudcexch_LDADD = $(LIBSVC) $(LIBTT) -lXm $(XTOOLLIB) ${X_LIBS} \
+dtudcexch_LDADD = $(LIBSVC) $(LIBTT) $(XTOOLLIB) ${X_LIBS} \
                 $(FONTEDT_PATH1)/libfuty/liboakfuty.a \
                 $(FONTEDT_PATH1)/libfal/libfal.a
 
@@ -14,10 +14,6 @@ if SOLARIS
 dtudcexch_LDADD += -ldl -lgen
 endif
 
-if AIX
-dtudcexch_LDADD += -ldl -liconv
-endif
-
 if FREEBSD
 dtudcexch_LDADD += -liconv
 endif